Cd r is short for cd recordable the discs are also known as worm media which stands for write once read multiple the advantage of cd r over other types of optical media is that you can use the discs with a standard cd player a related technology called cd rewritable cd rw allows you to erase discs and reuse them but the cd rw media does not necessarily work in all players as technology has changed since certain models were brought out the mechanical specifications of verbatim media ar