I have noticed these two words being confused more frequently of late, hence a grammar guerilla post. Your is the possessive of you. It means that something belongs to you.
“I see that your ball rolled into the street.”
“The house is yours but the front lawn is mine.”
“Your hair is beautiful. I wish I had some.”
By contrast the word you’re is a contraction formed from the words, you and are. Its meaning is quite distinct from that of your:
“You’re the best Husker fan in Nebraska.”
“You’re a regular reader of the Heidelblog.”
“You’re on the road to adopting the confessional Reformed theology, piety, and practice.”
In each of the last three examples we may substitute you are in place of you’re and say the same thing. In none of the six cases above may we exchange your and you’re.