Most leagues are for clubs to compete against each other. Some leagues are only for national teams, like World League, but others are open for any club to enter, like Club Wars.
Other leagues, like the Not So Pro Chess League, see players choose to join themselves and then organize into teams, instead of just joining a club that the owner chooses to register for a league.
Hello, can someone explain what country leages are on chess.com?
there are a lot of clubs like this, featuring "World league". What is that?