[blub]

when you buy a game you will get an code(key) and afther you log on a account you can just add it to your games by clicking on the top games->activate a product on steam and then typing the code

once you confirm it you will be able to download the game (or you can just copy to steamapps and relog and the steam will detect your game)

the newest of counter-strike series is counter-strike source

i have both of those games and source has better graphics although i'm a fan of cs 1.6 and still i play it more then the CS:S