Very often now I have seen sources.list files (including my own) that contain lines like these:deb     http://security.debian.org/         testing/updates main contrib non-freedeb     http://security.debian.org/         wheezy/updates  main contrib non-freedeb     http://http.debian.net/debian       wheezy-updates  mainI understood the meaning of the components (main, contrib and non-free). I also partially understood the meaning of the distribution (wheezy, testing, stable etc.) and that of the path. This is all well documented in the wiki.But what does the /updates or -updates mean?Should I write it with - or / myself?How am I supposed to know that?
stable, stable/updates and stable-updates in the sources.list
debian;upgrade;deb
Here is an explanation of the three source URIs you have listed.wheezy-updates: See the StableUpdates page on the DebianWikiAs the page explains, This path will be used for updates which many users may wish to  install on their systems before the next point release is made, such  as updates to virus scanners and timezone data.These were previously known as volatile.Both wheezy/updates and testing/updates are security fixes, to thestable release and testing respectively. Security fixes for testingare relatively recent, and supported on a best-effort basis.These correspond to the pages SecurityInformation for wheezy/updatesand security fixes fortesting for testing/updates.If you are asking why these have different forms, that is just how the people concerned choose how to have things set up. The / forward slash corresponds to the structure of the underlying URL, which in turn corresponds to the directory structure of the corresponding apt repository.So, for example the source URIdeb     http://http.debian.net/debian       wheezy-updates  maincorresponds to the URLhttp://security.debian.org/dists/wheezy/updates/the source URIdeb     http://security.debian.org/         testing/updates maincontrib non-freecorresponds to the URLhttp://security.debian.org/dists/testing/updates/the source URIdeb http://debian.lcs.mit.edu/debian/ wheezy-updates main contribnon-freecorresponds to the URLhttp://debian.lcs.mit.edu/debian/dists/wheezy-updates/