Casual-Fans are fans who aren't particularly into their fandom. They enjoy it, know some trivia, see some movies, have some stuff. Casual-Fans are more laid back.
Note: It is possible to be a Casual-Fan in one area, and a Proper-Fan in another. Or a Casual-Fan and a Psuedo-Fan, etc, etc.
Beth is a Casual-Fan of Star Wars, but a Proper-Fan of Star Trek. Things Star Wars Proper-Fans get annoyed about don't bother Beth, at least not enough to whine about.