They don't! Foamboard and foamcore are simple misspellings of the correct 'foam board' and Fome-Cor product name. Foam board and Fome-Cor are synonymous. All of these terms can be used to describe a foam sign in which your design or logo is printed directly onto the surface of the foam material. As noted above, our foam board signs are made with a foam center and paper-faced exterior for clear printing. The only minor difference may be the brand or actual material some sign shops might use when sourcing from the manufacturer or wholesaler. They are 3⁄16' thick, but custom thicknesses can be ordered by contacting us. Regardless of which name or term you might use we'll understand that you want a foam sign!