In economics, aggregate demand is the total demand for final goods and services in the economy (Y) at a given time and price level. It is the amount of goods and services in the economy that will be purchased at all possible price levels. This is the demand for the gross domestic product of a country when inventory levels are static. It is often called effective demand or abbreviated as 'AD'. In a general aggregate supply-demand chart, the aggregate demand curve (AD) slopes downward (indicating that higher outputs are demanded at lower price levels). An aggregate demand curve is the sum of individual demand curves for different sectors of the economy. The aggregate demand is usually described as a linear sum of four separable demand sources. 

Where C is consumption

I is investment

G denotes Government Spending

X - M = Net export

These macrovariables are constructed from varying types of microvariables from the price of each, so these variables are denominated in (real or nominal) currency terms.