Socket insert is a term used to describe a device that is used to connect two components together. It consists of a socket, which is a receptacle that holds the PLUG, and an insert, which is a device that is inserted into the socket. The most common example of a socket insert is a PLUG and BULB combination, where the PLUG is inserted into the socket and the BULB is inserted into the PLUG. This combination is used to provide electrical power to a device.