In the world of 'official tennis', there are four 'major' tournaments around the world: Wimbledon, in UK, the French Open, US Open and Australian Open.
A person who wins all four of these tournaments in a calendar year has won the Grand Slam. Sometimes each of these events is referred to as a 'Grand slam event' - so the terminology used by some writers and journalists is not always specific enough to be certain exactly what they are referring to unless the reader knows something of the history of these events.
As to those who have won them, I will just refer to singles events, though doubles and mixed-sexed doubles also have to be considered to give a complete answer.
In terms of males, Rod Laver has won two: 1962 and 1969. He is the only player to have done so. Don Budge was the first to win the Grand Slam in the 1930's.
These are the only two male players to ever win the true Grand Slam.
In terms of female players, only Maureen Connolly, Margaret Court and Steffi Graff have won the Grand Slam.
The first amateur to win a grand slam in tennis was Don Budge. He was an American from California, and won the event in 1938.
The doubles pair who have won the most Grand Slams is Bob Bryan and Mike Bryan. Todd Woodbridge and Mike Woodforde have also won a large number of Grand Slams.
No person from India has ever won a Grand Slam.
Caroline Woznjacki didn't win Grand slam titles
Jimmy Connors and Andre Agassi are two former, top US players who won 8 singles Grand Slam titles.However, the question does not stipulate whether the grand slams need to be only singles, or whether they are just Grand Slam titles[period]. There may be others, male or female, who won 8 Grand Slams, inclusive of singles, doubles and mixed doubles titles.
John Patrick McEnroe was the American tennis player who won 7 grand slams in the 1970s and 1980s.
She has won 5 Grand Slam titles
She has won 5 Grand Slam titles
The two most prolific are Australian "tennis stars". In terms of singles Calendar Grand Slams, Rod Laver has won two: in 1962 and 1969. Overall, however, Margaret Smith-Court has won the most Calendar Grand Slams of the lot, as she achieved the feat in singles in 1970 and achieved mixed doubles calendar Grand Slams on two or three other occasions. I suppose you might say that makes her the top star of true Grand Slam-making! In terms of Slam events, she has been awarded a total of 64 - 62 she won outright and two she holds jointly when no final was able to be played at the event.
Pete Sampras has the most Grand Slams with 14.
Roger Federer has 17 career grand slam titles.
Margaret Smith Court won 24 Grand Slam singles titles: 11 Australian Opens, 5 French Opens, 5 U.S. Opens, and 3 Wimbledon. She also won 19 Grand Slam doubles titles and 21 Grand Slam mixed doubles titles.