Men ages 25-27: Was he trying to get my attention by doing this, could he like me?

I've known him for about 5 years, not on a personal level, just through acquintances and some similiar interests. He saw me walking back to my car at the University, pulled up to me in his car, rolled down his window and said, "Just thought I would let you know that I think you're very pretty." Does that indicate interest...anything important lol? I am a good looking girl, but why did he feel the need to tell me is what I want to know. Keep in mind that I'm around 21...is that too big of an age gap difference for dating.