I heard some gay guys saying it and one guy said I'm a queen, then another guy said I knew that queen had an attitude the minute she walked in. What's a queen
A Queen is a gay man that is very dramatic, and high maintenance. They act like they own the world. They are Prima Donnas. You even hear two Queens fight and you will realize that they are very much like the 'popular' girl in school, and will even bitch slap each other, or pull hair. Being a Queen is an attitude. Alternately, a Queen can be a male that dresses up in women's clothes and makeup and performs on stage. Usually, gay, but not always. RuPaul is a Queen of this sort.
from the sounds of their vocabulary, it means a gay male who is very feminine, "fierce", and all the stereotypes of a gay male fashionita you can think of.
I think it depends a lot on region and context. Most of the time I hear it used it doesn't mean much beyond gay male and while it certainly isn't positive it is more dismissive than really insulting.
Watch the movie "The birdcage", a lot of the guys in there, especially the one who dressed up in drag where queens. I think the best way to think of it is as a person who fits all of the gay stereotypes.