I agree with the above advice. Perhaps you can take the time to read some of the stories on the site that have been awarded an Editor's Pick. They will give you an idea of how some of the best writers here introduce and describe their characters.
I think that many people will agree that they do not like reading what has come to be called a"laundry list" of character attributes, e.g. John was tall, dark, and handsome with washboard abs and hazel eyes. Mary was petite, brunette, had 34C breasts, narrow hips and green eyes.
You can find ways to work the description of your characters' looks and personalities within your story.
A prologue is usually about scene setting, not character setting. It may be an event that happens prior to the main story that is referenced in the story (e.g. some of the Bond opening sequences) or giving some background leading into the events of the story (e.g. the scrolls at the beginning of the Star Wars movies). Characters are better established in the opening paragraphs of the story proper.
I think the advice you're getting here is good. I've never seen a prologue that deals only with characters. Usually it has to do with some aspect of a character's past, a past event, or some other sort of scene-setting. But I think you have to ask yourself if that is best done in something like a prologue. Whatever you're explaining in the prologue is really some aspect of the story, even it's 'just' backstory. I've always thought that something like that is best done better and more naturally and unobtrusively when just worked into the flow of the story.
