An asset is something valuable you own that is not money in an account — land, a vehicle, equipment, an investment.

You record what it is worth, and that value feeds the "own" side of your net worth. Values drift, so an asset you have not revalued in a long time is flagged: a car entered at its purchase price three years ago is quietly overstating what you are worth.

Selling one is not income either. You are swapping a thing for cash of the same value, so only the difference from its recorded worth changes anything.