An electrical connector is a device that joins two or more electrical circuits together. Electrical connectors come in a variety of shapes and sizes, and are used to connect everything from small electronic devices to large appliances.
A wire harness, on the other hand, is a system of wires that are used to connect various components within a piece of equipment or machinery. Wire harnesses are typically used in vehicles and aircraft, but can also be found in industrial machines and other complex equipment.