What is the difference between foundation and concealer? Which do i get?

I'm still in high school and don't really like wearing make-up at all. But on those days when i get really bad bumps on my face i want to cover them up. Especially when they are red. They usually only come and go in one spot, otherwise i have a clear face. What is the best? I was looking at some neutrogena... show more I'm still in high school and don't really like wearing make-up at all. But on those days when i get really bad bumps on my face i want to cover them up. Especially when they are red. They usually only come and go in one spot, otherwise i have a clear face. What is the best? I was looking at some neutrogena products and they looked ok. Please help.