black•head noun \ˈblak-ˌhed\

"Blackheads are basically the same as whiteheads, except for blackheads have an oxidized fatty deposit. And when fatty deposits are oxidized, they turn dark. So they're called blackheads. When they're not oxidized, they're called whiteheads," Lancer says. "Blackheads differ from other pimples because they are open, and not enclosed by a layer of skin like most spots or pimples."