The "Law of Demand"

Notice that, in this example, the demand curve is downward sloping. That's a common-sense point: the higher the price, the less people will want to buy. In this case, common-sense has it 100% right.

Economists call this the Law of Demand:

At a higher price, the quantity demanded will be less, ceteris paribus.

(Ceteris paribus means: if nothing else changes to offset the change in price).

Some Jargon