Counter-strike was created by a man named
gooseman who was a big fan of
action quake and action quake II and wanted to see it brought to half-life. Even though a very crappy version of Action Half-life was made, CS remained the true succesor. It plays as counter-terrorists vs. terrorists and generally the objectives play as recover the
hostages or plant the bomb.
Lately though there has been an overwhelming amount of hackers in the game who destroy it. Allthough when you find a good server it can be a very enjoyable game.