The Football League is a league competition featuring professional football clubs from England and Wales, and is the oldest such competition in world football. Its 72 clubs are evenly divided into three divisions, The Championship, League One, and League Two. Promotion and relegation between these divisions is a central feature of the League and is further extended to allow the top Championship clubs to exchange places with the lowest placed clubs in the Premier League, and the bottom clubs of League Two to switch with the top clubs of the Football Conference, thus integrating the League into the English football league system. Although primarily a competition for English clubs, three clubs from Wales also take part.