Here 3-wire cable serves a split receptacle. The bottom half of the receptacle is controlled by a switch and the top half is always-hot.
An isolated-ground receptacle makes use of an extra wire for a separate ground in the circuit. This is the red wire in the 14/3 cable used here which is marked and connected to the grounding terminal on the receptacle. The other cable wires are connected as with any other circuit except for the ground wire. The bare copper ground wire is NOT connected to the receptacle, instead it is connected to the grounding terminal inside the electrical box where the receptacle is housed.
This page contains diagrams to add a new electrical outlet to an existing circuit. Arrangements are included to use an existing receptacle circuit or lights and switch circuits as the source for a new wall outlet.
A special isolated-ground receptacle is require for this circuit and can be identified by the orange color and a small triangle imprinted on the face. When connecting the wires, the isolated ground wire (the red wire pictured here) is marked with green tape or paint on each end and connected to the grounding bar in the service panel, and to the grounding terminal on the receptacle.