Your = a possessive adjective. It shows possession, that something belongs to the person you are talking to. e.g. This is not my pen, it is your pen.
You're = You are. It is a contraction (or short way of writing). e.g. You're crazy = You are crazy
gosh i want to thank euhm my english teacher for teaching me this
i hope this will help some people out. I ain't going to say names ...
swizzbeat
oh fuck i'm sorry