UF (underground feeder) is an NM cable which is specifically designed for wet locations and direct ground burial. When running wires underground or to outdoor projects, you need to use the UF cable. Another option electricians choose is using PVC conduit underground and pulling wires through.This type of cable is generally used for supplying outdoor fixtures and it contains insulated hot and neutral wire, plus a bare ground wire. Unlike the NM cable, the UF type has a solid plastic sheathing around each wire and has a gray outer sheathing. Additionally, this type of cable can be used for major circuit wiring.