When you get to know a band's music well enough that you want to know more about the actual band. Sources include anything you'll find doing a Google search.
Matt: I'm really digging Minus the Bear. I wanted to know where they got their name so I did some Band Homework on the Wikipedia machine and found out...
Dude: Yeah, found out what?
Matt: Hmmm, I forgot. Need to do more Band Homework. I never was good at learning.