A plug and socket is a device that allows an electrical appliance to be connected to the mains electricity supply. The socket is usually mounted on a wall or other surface, and the plug is inserted into it to make the connection. Plugs and sockets come in a variety of shapes and sizes, and are designed for use with different types of electrical equipment. Some plugs have a built-in fuse for safety, and some sockets have a switch that can be used to turn off the power to the appliance.