1. Aggregate demand is the total demand for final goods and services in an economy over a given period of time. It is made up of consumption, investment, government spending, exports minus imports.
2. Changes in aggregate demand are key to understanding economic fluctuations like recessions and recoveries. A rise in aggregate demand leads to economic expansion while a fall causes contraction.
3. Shifts in aggregate demand are caused by changes in factors like fiscal policy, monetary policy, business and consumer confidence, and external economic conditions.