Minor League Baseball is a level of professional baseball in North America. It is made up a many different teams which play in many leagues and levels of skill. Minor league teams are used by Major League Baseball (MLB) teams to have a place to put their players who they do not feel are skilled enough to play in the major leagues yet. They are also used to help injured major league players get ready to play in MLB again. These partnerships between major and minor league teams are called affiliations. Minor league teams generally play in cities that are too small for major league teams. City size usually increases with league level.