Fabulous means good-looking, attractive, extraordinary, etc. It is used when people find something to be one of the above terms and is occasionally used as a substitute for words like "cool" and "awesome". However, that is uncommon. ~Example sentences~ Wow, Stella looks fabulous in her new dress!
@haruuuuuka The word "dandy", when referring to a man, means that he devotes himself to style and fashion. Thus, by saying someone is "dandy and fabulous" you are saying that he/she is devoted to fashion and attractive.