I am sooo confused?? wut does all of this mean??

I was @ my friends bat mitzvah the other week, and i saw the guy i really like there. I was talking to my friend and all of a sudden he (the guy really like) comes up from behind me, puts his arms around my waist, hugs me really hard, and says hey i missed you. (i go to a different school noww) i am not very good @ flirting w/ guys so i just say hey i missed u 2. then we start talking and then his friend calls him over so he leaves. THEN he goes and hangs out w/ this other girl and sits on her lap. i am sooo confused... on facebook (and yes, i know i am too young to have a facebook...) we talk and he seems like he is flirting w/ me but im not sure... he was DEFINATELY flirting w/ me last semester (last year) but it sorta died down a bit... i am only 12... i really need help wut does all of this mean?? also any good flirting tips would be GREATLY appreciated!!! i definataly need help w/ that lol.... thanks!!!