What is the difference between a camera with a pinhole and a camera with a lens? (Holga cameras)?

I'm looking at Holga cameras; some have pinholes, some have a lens. I'm wondering what the difference is. I don't know how to create a long exposure with this camera, so any information you have on that would be appreciated as well. I basically want to know if there's a difference in the pictures; if so, what it is; and how to properly and effectively use each kind. Best answer gets 10 points & the satisfaction of helping me out!! :D