A human need is a state of deprivation of some basic satisfaction. People require food, clothing, shelter, safety, belonging, and esteem. These needs are not created by society or by marketers. They exist in the very texture of human biology and the human condition.
Wants are desires for specific satisfiers of needs. Although people’s needs are few, their wants are many. They are continually shaped and reshaped by social forces and institutions, including churches, schools, families and business corporations.
Demands are wants for specific products that are backed by an ability and willingness to buy them. Companies must measure not only how many people want their product but, more importantly, how many would actually be willing and able to buy it.
Marketers do not create needs. Marketers, along with other societal influences, influence wants. Marketers influence demand by making the product appropriate, attractive, affordable, and easily available to target consumers.
Philip Kotler (Marketing Management, 9th Edition)