A wall (from Old English weall) is a vertical structure, usually solid, that defines and sometimes protects an area. Most commonly, a wall delineates a building and supports its superstructure, separates space in buildings into sections, or protects or delineates a space in the open air. There are three principal types of structural walls: building walls, exterior boundary walls, and retaining walls.
A brick wall
Building walls have one main purpose: to support roofs and ceilings. Such walls most often have three or more separate components. In today's construction, a building wall will usually have the structural elements (such as 2×4 studs in a house wall), insulation, and finish elements or surface (such as drywall or panelling). In addition, the wall may house various types of electrical wiring or plumbing. Electrical outlets are usually mounted in walls.