@wanttoknow2,
I have both a quieter daughter and a louder daughter so I see both.
To me most people considered quiet are such because they are thinkers --- they tend to think through something rather than just jump into it and shout out their thoughts. They tend to be better listeners. Rather than yap -- they get things done; they tend to brag less and accomplish more as a result.
There is nothing that says because are quiet, they lack confidence, are shy or anti-social, are not good public speakers, etc.
My daughter takes drama and gets As in it. She has been on stage and speaks loud and clearly when on stage or giving presentations.
Recently her sports team in high school was required to do a fund raiser -- the goal was to sell a certain number of these fund raising items by the end of the weekend. Only her and another what you would classify a quiet girl met that goal -- this was not to family -- she went to youth games and approached parents as well as went around the neighborhood. Doesn't sound like someone shy or anti-social.
She is just that - quiet. I define her quietness as a quiet confidence.