A shift in the entire demand curve so that at any given price, people will want to buy a different amount. A change in demand is caused by some change other than a change in the goods price.
A change in demand is a change in consumers' willingness and ability to purchase products which occurs when some influence on those plans (other than the price of the product) changes. It is illustrated by a shift of the demand curve and by the creation of a new demand schedule. Contrast with change in the quantity demanded.