HE'S ASKING ME OUT!?!?!?

Hey, so I'm in a bit of a dilemma.. a guy in my history class that I do not fancy sent me a message on Facebook last night. I hardly know the kid and so it was a little surprising. I am friends with one of his friends though, so when he asked me if I'm going to prom with anyone (on Facebook), I thought he was asking for his friend. But I'm not going, so I messaged back saying basically "I'm not going, sorry, you could still find a date, but if it's too late, you can still go with friends and meet up with someone there." And he's like, "true." Then this morning before school, he messaged back, (which I just read right now, after school!) saying "Also, I was wondering if you wanted to just go out with me, not to prom, just a normal date." What am I supposed to say?! For God's sake, he's asking me out on FACEBOOK. What does that say about him?! Would our relationship/date be reliant on texting and messaging or whatever?! I've been through that once, never would I choose that again. &He's so shy- to the point where he doesn't even say hi back if you say hi to him first in the hall, just saying hi. I wouldn't want to go out with someone who is that shy! I hardly know the kid. In fact, when he messaged me I didn't even think he'd have remembered my name! We don't talk like normal friends would. He is not my type, and to be honest, I'm not looking for a boyfriend or anything, so.. please give me any advice.