Final answer:
Sebum is the oily substance secreted by the skin's oil glands that lubricates the hair and skin. It waterproofs, prevents water loss, and has antibacterial properties.
Step-by-step explanation:
Sebaceous glands, found all over the body, secrete an oily substance called sebum that lubricates and waterproofs the skin and hair. It prevents water loss, inhibits the growth of microorganisms, and has antibacterial properties. Sebum is secreted into hair follicles and makes its way to the skin surface.