An axon is a long, slender projection of a neuron that transmits electrical impulses away from the cell body. It plays a crucial role in the nervous system by connecting neurons to other neurons, muscles, or glands. Axons can vary in length, with some extending over a meter in humans, allowing for communication across long distances in the body. The axon is covered by a protective layer called the myelin sheath, which helps speed up the transmission of signals. This sheath is made up of specialized cells, such as Schwann cells in the peripheral nervous system and oligodendrocytes in the central nervous system.