Single-ended signaling is the simplest and most commonly used method of transmitting electrical signals over wires. One wire carries a varying voltage that represents the signal, while the other wire is connected to a reference voltage, usually ground. The main alternative to single-ended signaling is called differential signaling.
Single-ended signaling is less expensive to implement than differential, but it lacks the ability to reject noise caused by: differences in ground voltage level between transmitting and receiving circuits, and induction picked up on the signal wire.
The main advantage of single-ended over differential signaling is that fewer wires are needed to transmit multiple signals. A disadvantage of single-ended signaling is that the return currents for all the signals share the same conductor, and this can sometimes cause interference between signals.