Bots are NPC (non-player character) whom act like players. For history of Bots, look at Counter-Strike Wiki. You do not have Internet? Or (enough) friends to play with? Or you want single-player game where you shoot those bastards planting bomb in your neighborhood? Or become the bomb-planting bastard? Again, Warning for USA citizens: This is not encouraging for anyone to start planting a bomb in real-life. But it is fun in the game. What is it important on those bots? They need to act like players. For both better enjoyment and training. I recommend you to look at my page about Artificial Intelligence and primary to Human Behavior part. Do some testing with your AI before adding it to the game. Bad AI may ruin it all (you can still leave API for your community). And also in CS:GO, you can take control over bots to play when you are dead.