The Bechdel test comes from a comic by Alice Bechdel, in which two characters discuss female characters and how shows revolve around men. In order to pass the test a book/film/etc must pass three simple rules:
It has to have at least two women in it
Who talk to each other
About something besides a man
It doesn’t mean that the things is good by default or anything, so a good film may not pass the test while a brutal book may. It’s just an indication of the role of women in the media.