Confluence means a flowing together. In a literal sense, it's about rivers. But it's more often used to talk about the coming together of factors or ideas, or of cultures in a diverse city.
Con- means "with," and -fluence sounds like "flow." When things come together like rivers do, flowing from entirely different places, you call that a confluence. If the senior class needs to raise money for a class trip, and the drama club is looking for someone to do concessions during intermission at the school play, that's a confluence of factors.