Aluminum foil is made entirely of aluminum.  It is essentially aluminum ingots that are squished between beefy rollers. The thinner you want the foil, the tighter the rollers squish it.

Aluminum replaced tin for foil largely after WWII.  Tin did the same sort of thing but left food with a bit of an aftertaste, so production switched to aluminum.  Sometimes you still hear people call it "tin foil" for that reason.

Technically, a lubricant is sprayed on the foil to keep it flat, but generally it burns off.  In some types of aluminum foil (for specific industrial uses) not all the oil is burned off, but I don't think you would call this an "ingredient" in aluminum foil because it is not always there and is in a minute quantity.