Drywall is also known as a plasterboard or a Gypsum board.It is used for finishing purposes during the construction of interior walls and ceilings. There are many different types of drywall, suitable for use in various areas. The best drywall type to use in a bathroom is a greenboard. It is a drywall that provides moisture resistance as it contains an oil based additive. You can also use a Durock or a concrete backerboard which is more water resistant than a greenboard.