What does it mean when a guy gives you a back pat?

Answer 1

If you're a girl it means he's confused. If you're a guy it means he likes you.

Guys are schooled in not showing physical intimacy - hugs, stroking, holding hands and so on - to each other. They still feel close and caring though, so the expression of it often takes on mock-violent forms. They punch each other on the shoulder, pat backs and do high fives. Its violent, but its caring. You've surely seen it.

So, assuming you're a girl, you probably got a back-pat when what he really meant was "hug".

Of course, if you aren't that close, the whole boy-girl physical intimacy thing comes into play - clearly he shouldn't hug you so a back pat is a nice neutral way to say the same thing.