Wendy - there are no dumb questions except, maybe, the one's you don't ask.
A broody hen is when a girl decides she wants to sit on and hatch eggs. She can go broody whether there is a Rooster or not. However, unless there was a Rooster with her the eggs won't be fertile and thus cannot hatch.
You can get fertile eggs from someone elses chickens and put them under your broody to hatch. Broodies will even hatch other fowls eggs (ducks, etc.)
She will sit on the eggs until they hatch (normally 21 days) and then raise the chicks. Most broody mommas are very attentive to their young, sometimes you get one that just doesn't get it though.
If you don't have fertile eggs and don't want to hatch any then you can either let her sit on nothing or try and get her out of being broody (not easy to do from what I've learned). The best way seems to be to put a broody hen in a wire dog type kennel with no nesting material just food and water. After a week or so she should give up and snap out of it.