Myelin is the fatty tissue that protects the axon and gives nerves their whitish colour.
Step-by-step explanation:
The nerve fibers in our 'body' are enclosed by a sheath called Myelin. It has a dual function it gives color to the white matter and guards the nerve fibers against injuries. It also increases the transmission of electrical nerve signals across axons. Axons are extensions of nerve cells called neurons. White matter in the areas of our 'Central Nervous System' are mainly prepared by axons which are also referred to as tracts. White matter is responsible for learning abilities and other brain activities like coordinating message between different parts of the 'brain'.