Before talking about APIs as products, it is important to first understand what products actually are in the real world, how they are classified, and how they are perceived by buyers. According to many definitions, a product is any good and/or service that satisfies a need (a lack of a basic requirement) or a want (a specific requirement for products or services to match a need) and thus can be offered to a market. From a customer standpoint (someone who acquires the good or service: the buyer), a product is something that delivers a benefit, as otherwise there would be no point in acquiring it.
Products can be tangible or intangible. Tangible products are physical goods (objects), such as phones, cars, drones, ...