it's the GabeN world, once you enter it, there's no way of coming back. if u have money trust me u'll be getting eaten by the GabeN monsters which will take over ur wallet, credit card, bank account and any other shit where u carry ur money
In all seriousness, it's one of the best game store and best DRM out there with highest discount on almost every games. There are 3 large sale (didn't count the midweek, weekly, daily, special event, developer sales) which is Summer, Autumn and Winter sale which is having about 33-90% discount on all the great games. There's a limitation like you need to be logged in to Steam in order to sync your game's data (Steam Cloud functionality), chatting with friends, logging your hours of play, achievements, etc is required although you can still run in 'Offline mode' which still lets the gamer enjoy playing their games. Almost every game is unable to load without Steam being running which means you cannot run the following copy of the game without logging into your account and the account must need to have that game. All the games are up-to-date on Steam which means you can change your setting at anytime you want, whether you want your game to be up-to-date or just wanted to leave it as it is like. Tons of early access games are available to play, which are under construction games but yet available on Steam to try them out (most of them are buggy as hell so don't expect them to be perfect).
There is actually alot more you cannot even imagine.
Anyway,
http://www.reddit.com/r/Steam/ the perfect place for Steam related questions, news and related stuff (also you can check out Steam Community for instance, there are even specific discussion forums for every games on Steam)
If you're still looking for discounts, check out sites like
G2A,
Humble Bundle,
IndieGala,
Bundle Stars, etc who provide really great deal on Steam games (Keys which are only redeemable on Steam DRM).
Any more question, add me on Steam (check my signature)