Per the article it

measures representation of women in films and other works of fiction. Basically, a story passes the Bechdel test if it includes two female characters having a conversation about something other than a man

The idea is to have an analogous test for discussion of climate in a movie or TV episode

A not-that-serious test if a film meets the absolutely most basic criteria regarding female roles in the story.

Are there at least two women (in newer versions also: do they have a name)? Do they talk to each other instead of only to men? Do they talk about anything but a man?