The pool pass is a event that lasts for 3 weeks, it gives rewards from you earning Pool Pass points.
Pool Pass points
You can earn pool pass points by completing missions, winning games, and sometimes, win streaks. There are a total of 35 rewards you can get. Each reward costs 250 pool pass points.
Pool Pass premium
You can get the Pool pass premium for more rewards. It costs 4.99$! Pool pass premium awards are way better then regular rewards, for example, Legendary boxes, huge amounts of coins, epic boxes, golden shots, golden spins, cue pieces, and avatars.
If you received all rewards and have the pool pass, you can unlock some bonus boxes, these can contain some cue pieces and coins. However, you need 1500 Pool points per bonus box and there are only 15 of these. If you collected all rewards with 15 bonus boxes, you got all the rewards of Pool Pass (season) and Pool Pass will display as "max level".