Sebum is a component of the oil found on your skin. While "oil" on your skin refers to the overall mixture of substances, sebum is a specific type of lipid produced by the sebaceous glands. It's primarily responsible for moisturizing and protecting your skin.
In addition to sebum, skin oil also includes sweat and other substances that build up on your skin.
Therefore, sebum is just one part of the larger picture of skin oil.
