Periods represent a certain amount of time in the game. When a period ends, you'll earn a Highest Rank Prize based on your highest League Rank.

In addition to your Solo prize, you can also get a Highest Rank Prize from Tag Teams. If you have multiple Tag Partners, you'll get the Highest Rank Prize for your highest-ranked Tag Team at the end of a period.
*If you have more than one team that reached the same Rank, you'll only get the prize for one of them.