Wikipedia - Minor League Baseball

Minor League Baseball (MiLB) is a professional baseball organization below Major League Baseball (MLB), including teams affiliated with MLB clubs.

Entering the 2021 season, the number of full-season MLB-affiliated minor leagues with teams in the United States and Canada was reduced to 11, with a total of 120 teams (four per each of the 30 MLB franchises). There are also two affiliated rookie leagues based in the United States, with teams based at the parent clubs' spring training complexes in Arizona and Florida, and one affiliated rookie league in the Dominican Republic.