Drywall, also known as Plasterboard, Sheetrock, wallboard or Gypsum Wallboard is a panel made of gypsum plaster pressed between two thick sheets of paper. It is used to make interior walls and ceilings. Sheets are usually 4 feet by 8 feet and come in thicknesses ranging from 3/8", 1/2" and 5/8".
Drywall can be secured to the wall or ceiling studs with drywall nails, screws or drywall clips or stops. The seams are concealed using joint or fibre tape and several layers of joint compound (also called mud or spackle). Joint compound is also applied to all screw or nail holes. The entire wall or ceiling may be given a "skim coat" of joint or finishing compound to provide a smooth, finished surface.
Water Damage and Mold Growth on Drywall: Drywall is extremely pourous substance that supports the growth of mold and is easily damaged by exposure to water. Water will cause drywall to swell and disintegrate -- requiring replacement.
In areas that are expected to have a high humidity or exposure to water; i.e. kitchens, bathrooms and laundry rooms, Greenboard or cement board is used.
If water damage does occur, the area should be cut out, new sheetrock installed, spackled, primed and painted.