The Baseballs are an additional rewards from the spin wheel that grant extra points for the current League. and although they come from the spin wheel, these aren't boosters and don't count toward anything else outside the League event.

The Leagues are a ranking system, and allow you compete against other players within a Season.

The Seasons consists of a fixed period of time (approx. 2 weeks); within that time, players can compete with other players in the same League to earn the most points (which are determined by the number of Baseballs you collect). These points can also be earned by playing regular content and VIP levels.

Players that earn the most Season points in their League can also move to a more higher League, where you get better end-of-Season rewards as well and the value of the pre-level reward spinner Baseballs points goes up, as well.