How is the demand for a product different from just wanting it?

In economics, a mere wish or desire becomes demand only when three conditions are met together: you must want the good, you must have the money (purchasing power) to buy it, and you must be willing to spend that money on it. So wanting a new phone is just a desire. It becomes demand only when you can afford it and are actually ready to pay the price for it. That is why economists define demand as the quantity of a good a buyer is willing and able to purchase at a given price during a given time. A poor person may want a car badly, but with no purchasing power it stays a want, not demand. This is why advertisers target people who both desire a product and can pay for it.