Whats the difference between speaker ranges?

2.0 - basic stereo L and R speakers, 2.1 - same L and R speaker but now a subwoofer is added to take over the low end. 5.1 - usually for movies and games as this adds 2 rear channels, and most importantly a center channel. usually this is where most of the sound will come from because most sound from movies is talking. there is also 7.1 that adds 2 MORE rear channels and 8.1 that adds a center channel in the back. but no one really puts out any movies with 7.1 or 8.1 sound. at least not yet