A nerve is an enclosed, cable-like bundle of axons (the long, slender projection of a neuron). Neurons are sometimes called nerve cells, though this term is technically imprecise since many neurons do not form nerves, and nerves also include the non-axon glial cells that ensheath the axons in myelin.
Anatomy
Nerves are part of the peripheral nervous system. Afferent nerves convey sensory signals "to" the central nervous system, for example from skin or organs, while efferent nerves conduct stimulatory signals "from" the central nervous system to the muscles and glands. Afferent and efferent axons are often arranged together, forming mixed nerves. For example, the median nerve controls motor and sensory function in the hand.Billions of long nerve cells, called neurons,make up the bodies's nervous system. Neurons receive and transmit chemical-electrical messages to and from the brain. Each neuron is long and thin. One end receives messages and the other transmits the message to
Source:
http://en.wikipedia.org/wiki/Nerve