As I understand it, crafting a set of regular Steam Trading Cards gets you a common Game Badge. I also know that it is impossible to use a mix of regular and foil cards to craft a badge. Either you craft them entirely with Foil Cards, or you use no foil cards. (With the former granting you a Foil Badge instead).
Are Foil Badges instead of or in addition to regular badges? If the former, can you mix and match Foil / Regular levels? What happens?