I love to play the racket sport, tennis! Have you ever had a singles or doubles match?
I never have but I always was very curious!
The players have rackets strung with a cord. They use a hallow ball made of rubber and hit it over a net. It's a fun gameQ
and that is played indoors right?
It can be played indoor or outdoors. The game has connections with other lawn games like croquet or bowling. 
oh okay cool! I would always go see my dad play but he never let me because it was fast paced
Thats too bad. You can always try it now. The rules have been the same pretty much ever since 1890s. It's changed little since then.
I think I will how many materials do I need to buy for the sport?
You can probably rent everything you need. But basically just a racket and a ball. Decent gym shoes are a plus. The game originated in England in the 19th century. They didn't have anything fancy to use back then!