not being a basketball player myself I was wondering about this as well i the beginning.
In the meantime I learned this means the following:
when a team commits 4 fouls in 1 quarter, the opposing team gets the bonus.
This means that if a player in the bonus team gets fouled the next time, he takes 2 free throws, even if the foul was not commited on a shot attempt.
Also, should you not know about it either:
When a technical foul is called, the team who took the free trows gets ballposession after the free throws (normaly after the free throws the team that did not take the free throws gets the ball, or if the last free throw is missed there is a rebound situation, with the technical foul, there is no rebounding, the team taking the free throws gets the ball.
hope this helps.
They are not your friends; they dispise you. I am the only one you can count on. Trust me.