What exactly does "personality" mean?

The truth about that is when someone says she has a good personality, that usually means she's not pretty, but she's fun to be around, she has a good personality, when a girl is pretty a guy will say she's hot and she has a great personality.

You just explained your Personality!
"I have a personality, but I don't really like to put myself out there. "
That already says a lot about you! I bet that you are the kind of person who has trouble meeting new people, but once you get to be more comfortable with them, your relationship flourishes. You're a great person and you know it, but sometimes you are overly modest or maybe shy, even. I had this same problem, all you have to know is that the more confidence you have, the more people will like you. BUT you HAVE to be careful not to overdo it! You don't want to be known to have dreaded characteristic of "Bitchy". If you do overdo it though, you can always pass it off as a joke (Hey, it works for me! )
Hope I helped!

Most guys I know find girls like the one you're describing to be obnoxious and annoying. Or easy. There's nothing wrong with having a reserved personality, it shows that you're comfortable being you with or without everyone's attention. Different guys like different personalities. It doesn't mean that a girl doesn't have a personality if she's not an attention whore.