What's an Exchange-Traded Fund (ETF)?
Wikipedia has a fairly detailed explanation of ETFs.  http://en.wikipedia.org/wiki/Exchange-traded_fund ETFs offer the flexibility of stocks while retaining many of the benefits of mutual funds. Since an ETF is an actual fund, it has the diversification of its potentially many underlying securities. You can find ETFs with stocks at various market caps and style categories. You can have bond or mixed ETFs. You can even get ETFs with equal or fundamental weighting. In short, all the variety benefits of mutual funds. ETFs are typically much less expensive than mutual funds both in terms of management fees (expense ratio) and taxable gains. Most of them are not actively managed; instead they follow an index and therefore have a low turnover. A mutual fund may actively trade and, if not balanced with a loss, will generate capital gains that you pay taxes on. An ETF will produce gains only when shifting to keep inline with the index or you yourself sell. As a reminder: while expense ratio always matters, capital gains and dividends don't matter if the ETF or mutual fund is in a tax-advantaged account. ETFs have no load fees. Instead, because you trade it like a stock, you will pay a commission. Commissions are straight, up-front and perfectly clear. Much easier to understand than the various ways funds might charge you. There are no account minimums to entry with ETFs, but you will need to buy complete shares. Only a few places allow partial shares. It is generally harder to dollar-cost average into an ETF with regular automated investments. Also, like trading stocks, you can do those fancy things like selling short, buying on margin, options, etc. And you can pay attention to the price fluctuations throughout the day if you really want to. Things to make you pause: if you buy (no-load) mutual funds through the parent company, you'll get them at no commission. Many brokerages have No Transaction Fee (NTF) agreements with companies so that you can buy many funds for free. Still look out for that expense ratio though (which is probably paying for that NTF advantage). As sort of a middle ground: index funds can have very low expense ratios, track the same index as an ETF, can be tax-efficient or tax-managed, free to purchase, easy to dollar-cost average and easier to automate/understand. Further reading:
No ETN or ETF yet. There are beta funds, that aim to track the market.  What's really needed is a liquid market for cat risk trading/transfer, enabling users to buy protection, or take the other side.  You can write cat swaps, so derivative forms, including ILW's or with parametric triggers. But these aren't liquid at all yet.  Cat bonds are most liquid, but it dries up pretty quickly when events threaten as there's no true hedging market yet. ETF is essentially a stock, from accounting perspective. Treat it as just another stock in the portfolio. index ETF tracks indented index (if fund manager spend all money on Premium Pokemon Trading Cards someone must cover resulting losses) Most Index ETF are passively managed. ie a computer algorithm would do automatic trades. The role of fund manager is limited. There are controls adopted by the institution that generally do allow such wide deviations, it would quickly be flagged and reported. Most financial institutions have keyman fraud insurance. fees are not higher that specified in prospectus Most countries have regulation where fees need to be reported and cannot exceed the guideline specified. at least theoretically possible to end with ETF shares that for weeks cannot be sold Yes some ETF's can be illiquid at difficult to sell. Hence its important to invest in ETF that are very liquid. A closed-end fund is a collective investment scheme that is closed to new investment once the fund starts operating.  A typical open-ended fund will allow you to buy more shares of the fund anytime you want and the fund will create those new shares for you and invest your new money to continue growing assets under management.  A closed-end fund only using the initial capital invested when the fund started operating and no new shares are typically created (always exception in the financial community).  Normally you buy and sell an open-end fund from the fund company directly.  A closed-end fund will usually be bought and sold on the secondary market. Here is some more information from Wikipedia Some characteristics that distinguish a closed-end fund from an ordinary open-end mutual fund are that: Another distinguishing feature of a closed-end fund is the common use of leverage or gearing to enhance returns. CEFs can raise additional investment capital by issuing auction rate securities, preferred shares, long-term debt, and/or reverse-repurchase agreements. In doing so, the fund hopes to earn a higher return with this excess invested capital. "What does ETFs have to do with this or Amazon?   Actually, investing in ETFs means you are killing actively managed Mutual Funds (managed by people, fund managers) to get an average return (and loss) of the market that a computer manage instead of a person. And the ETF will surely have Amazon stocks because they are part of the index.  I only invest in actively managed mutual funds. Yes, most actively managed mutual funds can't do better than the index, but if you work a bit harder, you can find the many that do much better than the ""average"" that an index give you." "Remember that in most news outlets journalists do not get to pick the titles of their articles.  That's up to the editor.  So even though the article was primarily about ETFs, the reporter made the mistake of including some tangential references to mutual funds.  The editor then saw that the article talked about ETFs and mutual funds and -- knowing even less about the subject matter than the reporter, but recognizing that more readers' eyeballs would be attracted to a headline about mutual funds than to a headline about ETFs -- went with the ""shocking"" headline about the former. In any case, as you already pointed out, ETFs need to know their value throughout the day, as do the investors in that ETF.  Even momentary outages of price sources can be disastrous. Although mutual funds do not generally make transactions throughout the day, and fund investors are not typically interested in the fund's NAV more than once per day, the fund managers don't just sit around all day doing nothing and then press a couple buttons before the market closes.  They do watch their NAV very closely during the day and think very carefully about which buttons to press at the end of the day.  If their source of stock price data goes offline, then they're impacted almost as severely as -- if less visibly than -- an ETF. Asking Yahoo for prices seems straightforward, but (1) you get what you pay for, and (2) these fund companies are built on massive automated infrastructures that expect to receive their data from a certain source in a certain way at a certain time.  (And they pay a lot of money in order to be able to expect that.)  It would be quite difficult to just feed in manual data, although in the end I suspect some of these companies did just that.  Either they fell back to a secondary data supplier, or they manually constructed datasets for their programs to consume." "Does the bolded sentence apply for ETFs and ETF companies? No, the value of an ETF is determined by an exchange and thus the value of the share is whatever the trading price is. Thus, the price of an ETF may go up or down just like other securities. Money market funds can be a bit different as the mutual fund company will typically step in to avoid ""Breaking the Buck"" that could happen as a failure for that kind of fund. To wit,   must ETF companies invest a dollar in the ETF for every dollar that an   investor deposited in this aforesaid ETF? No, because an ETF is traded as shares on the market, unless you are using the creation/redemption mechanism for the ETF, you are buying and selling shares like most retail investors I'd suspect. If you are using the creation/redemption system then there are baskets of other securities that are being swapped either for shares in the ETF or from shares in the ETF." Dividends are not paid immediately upon reception from the companies owned by an ETF. In the case of SPY, they have been paid inconsistently but now presumably quarterly. The ETF price quoted on the stock exchange is in principle not referenced to NAV. The fund administrator will calculate and publish the NAV net of all fees, but the ETF price you see is determined by the market just like for any other security.  Having said that, the market will not normally deviate greatly from the NAV of the fund, so you can safely assume that ETF quoted price is net of relevant fees. "As with ANY investment the first answer is....do not invest in any that you do not fully understand.  ETF's are very versatile and can be used for many different people for many different parts of their portfolio, so I don't think there can be a blanket statement of ""this"" one is good or bad for all." "The London Stock Exchange offers a wealth of exchange traded products whose variety matches those offered in the US.  Here is a link to a list of exchange traded products listed on the LSE.  The link will take you to the list of Vanguard offerings.  To view those offered by other managers, click on the letter choices at the top of the page.  For example, to view the  iShares offerings, click on ""I"". In the case of Vanguard, the LSE listed S&P500 ETF is traded under the code VUSA.  Similarly, the Vanguard All World ETF trades under the code VWRL.  You will need to be patient viewing iShares offerings since there are over ten pages of them, and their description is given by the abbreviation ""ISH name"". Almost all of these funds are traded in GBP. Some offer both currency hedged and currency unhedged versions.  Obviously, with the unhedged version you are taking on additional currency risk, so if you wish to avoid currency risk then choose a currency hedged version.  Vanguard does not appear to offer currency hedged products in London while iShares does.  Here is a list of iShares currency hedged products.  As you can see, the S&P500 currency hedged trades under the code IGUS while the unhedged version trades under the code IUSA. The effects of BREXIT on UK markets and currency are a matter of opinion and difficult to quantify currently.  The doom and gloom warnings of some do not appear to have materialised, however the potential for near-term volatility remains so longs as the exit agreement is not formalised.  In the long-term, I personally believe that BREXIT will, on balance, be a positive for the UK, but that is just my opinion." Bond ETFs are traded like normal stock.  It just so happens to be that the underlying fund (for which you own shares) is invested in bonds.  Such funds will typically own many bonds and have them laddered so that they are constantly maturing.  Such funds may also trade bonds on the OTC market. Note that with bond ETFs you're able to lose money as well as gain depending on the situation with the bond market.  The issuer of the bond does not need to default in order for this to happen.  The value of a bond (and thus the value of the bond fund which holds the bonds) is, much like a stock, determined based on factors like supply/demand, interest rates, credit ratings, news, etc. "Don't put money in things that you don't understand. ETFs won't kill you, ignorance will. The leveraged ultra long/short ETFs hold swaps that are essentially bets on the daily performance of the market. There is no guarantee that they will perform as designed at all, and they frequently do not. IIRC, in most cases, you shouldn't even be holding these things overnight. There aren't any hidden fees, but derivative risk can wipe out portions of the portfolio, and since the main ""asset"" in an ultra long/short ETF are swaps, you're also subject to counterparty risk -- if the investment bank the fund made its bet with cannot meet it's obligation, you're  may lost alot of money. You need to read the prospectus carefully. The propectus re: strategy. The Fund seeks daily investment results, before fees and expenses, that correspond to twice the inverse (-2x) of the daily performance of the Index. The Fund does not seek to achieve its stated investment objective over a period of time greater than a single day. The prospectus re: risk. Because of daily rebalancing and the compounding of each day’s return over time, the return of the Fund for periods longer than a single day will be the result of each day’s returns compounded over the period, which will very likely differ from twice the inverse (-2x) of the return of the Index over the same period. A Fund will lose money if the Index performance is flat over time, and it is possible that the Fund will lose money over time even if the Index’s performance decreases, as a result of daily rebalancing, the Index’s volatility and the effects of compounding. See “Principal Risks” If you want to hedge your investments over a longer period of time, you should look at more traditional strategies, like options. If you don't have the money to make an option strategy work, you probably can't afford to speculate with leveraged ETFs either." "I used to use etfconnect before they went paid and started concentrating on closed end funds. These days my source of information is spread out. The primary source about the instrument (ETF) itself is etfdb, backed by information from Morningstar and Yahoo Finance. For comparison charts Google Finance can't be beat. For actual solid details about a specific ETF, would check read the prospectus from the managing firm itself. One other comment, never trust a site that ""tells you"" which securities to buy. The idea is that you need sources of solid information about financial instruments to make a decision, not a site that makes the decision for you. This is due to the fact that everyone has different strategies and goals for their money and a single site saying buy X sell Y will probably lead you to lose your money." As keshlam said, an ETF holds various assets, but the level of diversification depends on the individual ETF. A bond ETF can focus on short term bonds, long term bonds, domestic bonds, foreign bonds, government bonds, corporate bonds, low risk, high risk, or a mixture of any of those. Vanguard Total International Bond ETF (BNDX) for instance tries to be geographically diverse.