The bonus pool encourages players to keep playing ranked games and improve their ranking. It makes the matchmaking non zero-sum, which in turn means its not a viable strategy to get to 1st on the ladder, and then sit there for 3 months while no one can approach your zenith.

In actual terms of mechanics, it is a bonus value added to your rank when you win. Extra earned rating will match, point for point, any rating you accrue from winning games, until the pool is empty.

It fills over time (maybe when not playing, specifically?)

The bonus pool encourages players to keep playing ranked games and improve their ranking. It makes the matchmaking non zero-sum, which in turn means its not a viable strategy to get to 1st on the ladder, and then sit there for 3 months while no one can approach your zenith.

In actual terms of mechanics, it is a bonus value added to your rank when you win. Extra earned rating will match, point for point, any rating you accrue from winning games, until the pool is empty.

It fills over time whether you are playing or not.