A drag queen is, at least in my mind, a man doing exaggerated impersonation of characteristics supposedly associated with being female including their modes of dress. Ru Paul would be a US example. Our own Paul O'Grady's Lily Savage persona would be another.
It's widely thought of as being a gay 'thing' though not exclusively so.
I don't follow
@icowden's assertion that it and trans are so separate as to be binary. There's a whole set of different forms of, for want of a better phrase, cross dressing which seem to me to be something like a continuum. Eddie Izzard seems to have gone from cross dressing comic, drag if not the full queen thing, to identifying as a woman.
Grayson Perry anyone?
Used to be a bloke at work who was called for many years (I think) Stuart. Over time he grew hair and nails and began to dress androgynously, eventually changing to the name Louise. No hormones, no surgery. Were they trans? I cannot remember whether the term was even widely used then - closing months of C20 when we were on a course together.