is a Model exactly the same as a Business Entity?

I've been programming for a long time now, and I have always seen Model classes exactly as a business entity. For instance: sales, users, products, orders, etc...

But I have come to certain source codes (specifically in MVVM applications in WPF) where Model not only include business entities, but several other types, and now I'm confused.

What exactly represents model classes, are they limited to business objects or what else do they include? If I could get a couple of examples, that'd be good.