RoboCup, as Maayan said, has several different leagues. I believe the final objective of the RoboCup competition is to create a team of humanoid robotic soccer players that can play World Cup-caliber soccer. Obviously, we are a long way away from that.

I currently work on the Small size robots. At present, they work as 5 players with a single brain. There is a camera above the field that is the vision sensor. A central computer takes that vision and does some calculations as for the predicted positions of various players and the ball. The computer runs this information through its strategy and tells the five robots (4 players, 1 goalie) what to do via radio communication. There are no sensors onboard the individual robots, and no high-level computing is done on the robots themselves. Everything is done through the centralized computer.