Nasdaq vs Nasdaq Trade Reporting Facility
"You can infer some of the answers to your questions from the BATS exchange's market data page and its associated help page.  (I'm pretty sure a page like this exists on each stock exchange's website; BATS just happens to be the one I'm used to looking at.) The Matched Volume section refers to all trades on a given date that took place on ""lit"" exchanges; that is, where a public protected US stock exchange's matching engine helped a buyer and a seller find each other.  Because there are exactly 11 such exchanges in existence, it's easy to show 100% of the matched volume broken down into 11 rows. The FINRA & TRF Volume section refers to all trades on a given date that took place on ""non-lit"" exchanges.  These types of trades include dark pool volume and any other trade that is not required to take place in public but is required to be reported (the R in TRF) to FINRA.  There are three venues via which these trades may be reported to FINRA -- NASDAQ's, NYSE's, and FINRA's own ADF.  They're all operated under the purview of FINRA, so the fact that they're ""located at"" NASDAQ or NYSE is a red herring.  (For example, from the volume data it's clear that the NASDAQ facility does not only handle NASDAQ-listed (Tape C) securities, nor does the NYSE facility only handle NYSE-listed (Tape A) securities or anything like that.) The number of institutions reporting to each of the TRFs is large -- many more than the 11 public exchanges -- so the TRF data is not broken down further.  (Also I think the whole point of the TRFs is to report in secret.)  I don't know enough details to say why the NASDTRF has always handled more reporting volume than the other two facilities.  Of course, since we can't see inside the TRF reporting anyway, it's sort of a moot point."
What you should compare is SPX, SPY NAV, and ES fair value.   Like others have said is SPX is the index that others attempt to track. SPY tracks it, but it can get a tiny bit out of line as explained here by @Brick .  That's why they publish NAV or net asset value.  It's what the price should be.  For SPY this will be very close because of all the participants.  The MER is a factor, but more important is something called tracking error, which takes into account MER plus things like trading expenses plus revenue from securities lending.  SPY (the few times I've checked) has a smaller tracking error than the MER.  It's not much of a factor in pricing differences. ES is the price you'll pay today to get SPX delivered in the future (but settled in cash).  You have to take into account dividends and interest, this is called fair value.  You can find this usually every morning so you can compare what the futures are saying about the underlying index. http://www.cnbc.com/pre-markets/ The most likely difference is you're looking at different times of the day or different open/close calculations. Different exchanges sometimes offer different order types, and of course have different trading fees.  But once a trade is finished, it should not matter where it was executed. It depends on what site you're looking on and what exchange they're pulling the data from. Even though funds and stocks are called the same thing, they have different ticker symbols in each country's exchange or could be traded as pink sheet stocks in the US. If a company or fund is based in another country (like Canada or the UK) they probably also trade on that country's exchange (Toronto or London) under a different symbol. This can cause a lot of confusion when researching these tickers. "If I buy the one from NSY, is it the ""real"" Sinopec? No - you are buying an American Depository Receipt. Essentially some American bank or other entity holds a bunch of Sinopec stock and issues certificates to the American exchange that American investors can trade.  This insulates the American investors from the cost of international transactions.   The price of these ADRs should mimic the price of the underlying stock (including changes the currency exchange rate) otherwise an arbitrage opportunity would exist.  Other than that, the main difference between holding the ADR and the actual stock is that ADRs do not have voting rights. So if that is not important to you then for all intents and purposes trading the ADR would be the same as trading the underlying stock." On NASDAQ the ^ is used to denote other securities and / to denote warrents for the underlying company. Yahoo maybe using some other designators for same. Electronic trading is many orders of magnitude cheaper and more liquid than floor trading and is rapidly displacing it. Stil, electronic trading accounts for 79% of stock trading volume in the U.S. Polcari is losing the battle. Floor trading is still offered, but it's only used for bulk orders, so electronic trading is servicing small trades at minimum prices while floor trading is now the concierge service. Interactive Brokers provides historical intraday data including Bid, Ask, Last Trade and Volume for the majority of stocks. You can chart the data, download it to Excel or use it in your own application through their API.  EDIT: Compared to other solutions (like FreeStockCharts.com for instance), Interactive Brokers provides not only historic intraday LAST**** trades **but also historic BID and ASK data, which is very useful information if you want to design your own trading system.  I have enclosed a screenshot to the chart parameter window and a link to the API description. "In the US, stocks are listed on one exchange but can be traded on multiple venues.  You need to confirm exactly what your data is showing: a) trades on the primary-listed exchange; or b) trades made at any venue. Also, the trade condition codes are important.  Only certain trade condition codes contribute towards the day's open/high/low/close and some others only contribute towards the volume data.  The Consolidated Tape Association is very clear on which trades should contribute towards each value - but some vendors have their own interpretation (or just simply an erroneous interpretation of the specifications). It may surprise you to find that the majority of trading volume for many stocks is not on their primary-listed exchange.  For example, on 2 Mar 2015, NASDAQ:AAPL traded a total volume across all venues was 48096663 shares but trading on NASDAQ itself was 12050277 shares. Trades can be cancelled.  Some data vendors do not modify their data to reflect these busted trades.   Some data vendors also ""snapshot"" their feed at a particular point in time of the data.  Some exchanges can provide data (mainly corrections) 4-5 hours after the closing bell.  By snapshotting the data too early and throwing away any subsequent data is a typical cause of data discrepancies.   Some data vendors also round prices/volumes - but stocks don't just trade to two decimal places. So you may well be comparing two different sets of trades (with their own specific inclusion rules) against the same stock.  You need to confirm with your data sources exactly how they do things. Disclosure: Premium Data is an end-of-day daily data vendor." "There are basically two different markets for ADRs and ordinary shares. 1) The American market, 2) the ""local"" market. The following is not true for most stocks in ""developed"" markets. But it is often true that the American market (for ADRs) is far more liquid than the local market for ordinary shares of a developing country. For instance, there was a time when the ADRs of Telmex (Telefonos of Mexico) was the fifth most traded stock in the world, after Exxon (before its merger with Mobil), IBM, Microsoft, and A T&T, meaning that it was easy to trade with low fees on the NYSE. It was much harder and slower to buy the local shares of Telmex in Mexico, on the Mexican exchange. Also, the accompanying currency transactions were harder to execute with the ord, because you have to settle in local currency and pay an FX commission. With the ADR, the exchange rate is ""built"" into the (dollar) price, and you settle in dollars." NYSE and Nasdaq are secondary markets where stocks are bought or sold. The process of creating new stocks via IPO or private placements etc are called Private Market. "To expand on keshlam's answer: A direct feed does not involve a website of any kind.  Each exchange publishes its order/trade feed(s) onto a packet network where subscribers have machines listening and reacting. Let's call the moment when a trade occurs inside an exchange's matching engine ""T0"".  An exchange then publishes the specifics of that trade as above, and the moment when that information is first available to subscribers is T1.  In some cases, T1 - T0 is a few microseconds; in other (notorious) cases, it can be as much as 100 milliseconds (100,000x longer). Because it's expensive for a subscriber to run a machine on each exchange's network -- and also because it requires a team of engineers devoted to understanding each exchange's individual publication protocols -- it seems unlikely that Google pays for direct access.  Instead Google most likely pays another company who is a subscriber on each exchange around the world (let's say Reuters) to forward their incoming information to Google.  Reuters then charges Google and other customers according to how fast the customer wants the forwarded information.  Reuters has to parse the info it gets at T1, check it for errors, and translate it into a format that Google (and other customers) can understand.  Let's say they finish all that work and put their new packets on the internet at time T2. Then the slow crawl across the internet begins.  Some 5-100 milliseconds later your website of choice gets its pre-processed data at time T3.  Even though it's preprocessed, your favorite website has to unpack the data, store it in some sort of database, and push it onto their website at time T4. A sophisticated website might then force a refresh of your browser at time T4 to show you the new information.  But this forced refresh involves yet another slow crawl across the internet from where your website is based to your home computer, competing with your neighbor's 24/7 Netflix stream, etc.  Then your browser (with its 83 plugins and banner ads everywhere) has to refresh, and you finally see the update at T5. So, a thousand factors come into play, but even assuming that Google is doing the most expensive and labor-intensive thing it can and that all the networks between you and Google and the exchange are as short as they can be, you're not going to hear about a trade -- even a massive, market-moving trade -- for anywhere from 500 milliseconds to 5 seconds after T0.  And in a more realistic world that time will be 10-30 seconds. This is what Google calls ""Realtime"" on that disclaimer page, because they feel they're getting that info to you as fast as they possibly can (for free). Meanwhile, the computers that actually subscribe to an exchange heard about the trade way back at time T1 and acted on that information in a few microseconds.  That's almost certainly before T2 and definitely way way before T3.  The market for a particular instrument could change direction 5 times before Google even shows the first trade. So if you want true realtime access, you must subscribe to the exchange feed or, as keshlam suggests, sign up with a broker that provides its own optimized market feeds to you. (Note: This is not an endorsement of trading through brokers.)" There isn't a single universal way to reference a stock, there are 4 major identifiers with many different flavours of exchange ticker (see xkcd:Standards) I believe CUSIPs and ISINs represent a specific security rather than a specific listed instrument. This means you can have two listed instruments with one ISIN but different SEDOLs because they are listed in different places. The difference is subtle but causes problems with settlement Specifically on your question (sorry I got sidetracked) take a look at  CQS Symbol convention to see what everything means 10-Q is the quarterly report, and accordingly is filed quarterly. Similarly, 10-K is the annual report. 8-K is a general form for notification of material events. It is filed every time a material event is required to be reported to the shareholders. It may accompany the periodical reports, but doesn't have to. It can be filed on its own. If you're only interested in the financial statements, then you should be looking for the 10K/10Q forms. SEC will tell you when the forms were filed (dates), but it won't tell you what's more material and what's less. So you can plot a stock price graph on these dates, and see what was deemed more material by the investors based on the price fluctuations, but be prepared to find fluctuations that have no correlation to filings - because the market as a whole can drag the stock up or down. Also, some events may not be required to be reported to SEC, but may be deemed material by the investors. For example, a Cupertino town hall meeting discussing the zoning for the new AAPL HQ building may be deemed material by the investors, based on the sentiments, even if no decision was made to be reported to SEC. No, it's not even remotely accurate in the current sense. Both markets have counterparties directly executing against one another, and both have auctions. The auction mechanics are different (with NYSE's Specialist/DMM model) but during normal market hours there isn't much difference. The issue with trading stocks vs. mutual funds (or ETFs) is all about risk. You trade Microsoft you now have a Stock Risk in your portfolio. It drops 5% you are down 5%. Instead if you want to buy Tech and you buy QQQ if MSFT fell 5% the QQQs would not be as impacted to the downside. So if you want to trade a mutual fund, but you want to be able to put in stop sell orders trade ETFs instead.   Considering mutual funds it is better to say Invest vs. Trade.  Since all fund families have different rules and once you sell (if you sell it early) you will pay a fee and will not be able to invest in that same fund for x number of days (30, 60...)