Tennis played with two players on each side is called doubles tennis.
for every grand slam match, it is best 3 out of 5 for men, and best 2 out of 3 for women
Pretty much all of the countries, considering that the Grand Slams take in the best players from each country in the world.
Pete Sampras and Roger Federer both have 14 grand slams each.
it is about 650 (i think)
There are countless professional tennis tournaments each year. There is no one extremely important tournament. The four grand slams (US Open, French Open, Wimbledon, and the Australian Open) are the biggest tournaments in tennis each year. in 2012 Novak Djokovic won the Australian Open and the three others have not been played yet.
A normal tennis set is first to 6 games. Each game is 4 points. A tennis set can last anywhere from 20 minutes to 2 hours or even more depending on how close the set ends up being.