There's a misplaced bracket (or brace, or even parenthesis, if you prefer) here. The Golden Slam is all four Grand Slam events and the Olympics, in the same calendar year. The question should read, "Who is the only player in tennis history to have won a golden slam (all four major titles plus an Olympic gold in the same year)?"
If we were being really pedantic, we could point out that the four biggest annual tennis tournaments (Wimbledon, plus the Australian, French and US Opens) are usually referred to as the Grand Slam tournaments; winning all four of them is the Grand Slam. This is why, if you win the Olympics as well, it's called a Golden Slam.
The Majors are in golf (The Open, the US Open, the Masters and the PGA).
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