Um wtf? Are you asking what sex is? Cause if you are then this isn't the right place to ask. Go ask in the Sex and Sexuality club. There are little kids on this site and a lot of little kids like Justin Bieber. So it's not the smartest idea asking a question like this here. Anyway if you don't know what sex is and your 13(i'm assuming your 13 or older cause you should be 13 years old to be here)then I don't know. I don't know any 13 year older who doesn't know what sex is. So if your not 13 please leave this site and come back when your old enough. If you want to know what sex is ask your parents! And This is? What do you mean?
First,Why do you ask this on a Justin Bieber spot?huh?
Second,Why do you ask such a question to totally unknown people?Ask it to your parents!
Third,How could you don't know what sex is,if you are 13!