The law of demand states that as the price of a good or service falls, the quantity demanded of that good or service will increase, and conversely, as the price of a good or service rises, the quantity demanded of that good or service will decrease. This means that there is an inverse relationship between the price of a good or service and the quantity demanded of it. In simpler terms, people tend to buy more of a product when it is cheaper, and buy less of it when it is more expensive.