Profits made from selling items other than inventory.
Susan has a shoe store. She bought shoes for $2,000 and sold them for $3,000. She bought Exxon stock for $1,000 and sold it for $1,500. The $500 profit on the Exxon stock would be a gain. The profit from the shoes would be listed under operating income because she earned that in the normal course of business, but the $500 profit from the stock would be a gain.