I'm currently trying to get either linux or unix but need to know what I need to do to be able to play my PC games.

It's possible to use PC on linux but they make lots of current games for that OS I would suggest using google and search that question you'll be surprised. My question you Cleric is why would you want to use linux when wanting to run PC games is there something better than XP whats the deal, Why did you choose this OS??

my teacher told me that unix and linux are used for servering.why don't you use windows?i think it's more better for playing games.

WINE allows some games to run under Linux, but sometimes its a pain to get working.

I'd suggest dual booting windows and linux, if games are a priority, but you still want to use Linux for whatever reason.