Nexball is ball sport game where 2 teams (red & blue) play against one another and try to score goals. You can’t shoot (/frag) other players here.
There are two Nexball game-types. The first is similar to soccer/football and allows the player to direct the ball by running into it. The second one is like basketball (or team handball) and allows the player to catch, carry, and shoot the ball. The basketball game-type also allows stealing the ball from an opponent.
Push the ball? Just move at it and the ball will jump in that direction.
Score a goal? Push the ball into the goal of the other team.
Catch or pick up the ball? Just run into the ball.
Steal the ball? Click or press alternate-fire while close to a ball carrier.