Nerves are part of the peripheral nervous system. Afferent nerves convey sensory signals to the brain, for example from skin or organs, while efferent nerves conduct stimulatory signals from the brain to the muscles and glands.
These signals, sometimes called nerve impulses, are also known as action potentials: Rapidly traveling electrical waves, which begin typically in the cell body of a neuron and propagate rapidly down the axon to its tip or "terminus."
Nerves may contain fibers that all serve the same purpose; for example motor nerves, the axons of which all terminate on muscle fibers and stimulate contraction. Or they be mixed nerves.