Simplify the following text for a Grade 17 native English-speaking person.
Original: The 2011 ATP World Tour calendar comprises the Grand Slam tournaments ( supervised by the International Tennis Federation ( ITF ) ) , the ATP World Tour Masters 1000 , the ATP World Tour 500 series , the ATP World Tour 250 series , the ATP World Team Championship , the Davis Cup ( organized by the ITF ) , and the ATP World Tour Finals .
Simplified: The 2011 ATP World Tour calendar cosists of Grand Slam tournaments ( organised by the International Tennis Federation ( ITF ) ) , the ATP World Tour Masters 1000 , the ATP World Tour 500 series , the ATP World Tour 250 series , the ATP World Team Championship , the Davis Cup ( organized by the ITF ) , and the ATP World Tour Finals .