The Grand Slam tournaments, also known as the majors, are the four most important annual tennis tournaments worldwide.
The Australian Open (played on hard court) is the first major of the year, taking place in mid-January, followed by French Open (played on clay) in May/June. Wimbledon, the only of the four majors to be played on grass, takes place in June/July, and the Grand Slam season finishes with the US Open (hard court) played in August/September.
Legendary Spanish tennis player Rafael Nadal currently tops the list of the most Grand Slam tennis titles won of all time by professional male tennis players. He edges two other legendary players, Serbian Novak Djokovic and Swiss Roger Federer both sit at 20 titles.
Details at ESPN
Source: ATP Tour, ESPN