Why are guys so hard to understand?

I've known this guy forever and a day. And he will come up and say 'Hi Mandy' and look at me every few minutes, but thats all the more he ever does. And then my brother can get him on web cam saying he likes me and so on, why? If he does why dosen't he just tell me? His friend has mentioned it a few times as well. But he never says a thing.