Tennis is a sport played with a racket and can be either one on one or doubles format.
I enjoy watching tennis but never tried to play it.  How long has tennis been around?
The modern version of game originated in England in the lase 19th century.
I guess that is why the sport is so popular over there.  Is that when Wimbledon started?
No but, the rules have change little since the 1890's
Do they tennis in the Olympics?
Yes it is an Olympic sport and is played by people of all ages everywhere.
I am sure most good players start playing really young.  
Yes, but it is an extremely accessible sport.  It can even be played by those in wheelchairs.