What is the difference between the ATP world tour, and the ITF (international tennis federation)? What is the difference between the rankings of the ATP and the rankings of the ITF?
ATP Tennis or The Association of Tennis professionals is the governing body of tennis in the men's circuit of professional tennis. It consists of all the tennis tournaments organized by the Association of Tennis Professionals or ATP. The organization is affiliated to the International Tennis Federation or the ITF, the international governing body of tennis. The ATP was founded in 1972 with aim of ruling the sport in the domain of men's tennis. Since then, the organization has been controlling various tennis events scheduled under ATP Tennis Tour.
ATP tennis tour schedule includes numerous tennis tournaments, which are held around the world throughout the year. Tennis tournaments included in the ATP Tennis schedule are divided in various groups. The main groups of tennis tournaments held under ATP Tennis are Grand Slams, Tennis Masters Cup, ATP Masters Series, ATP International Series, ATP International Series Gold, ATP Challenger Series, Satellites Tournaments and Futures tournaments. The Satellite Tournaments and Future Tournaments are contested as ITF events, which are included in the ATP Tennis schedule. Tennis Master Cup is also held in association with the ITF.
Ref :- Tennis Associations
In basic terms, the ATP organise the big events for the big players while the ITF hold the events for the players with much lower world rankings.