Answer and Explanation:
The aggregate demand and supply represents the cumulative total of the product demanded and supplied by all economic agents. While the supply demand studied by us in microeconomics relates to a single supplier or a single demand.
Just take an example for the competitive market supply curve for one company is
As we know that
p = mc
And,
p = q + 1
Therefore
q = p - 1
So if there are 1000 such companies on the market, Q= 1000p-1000 is the aggregate supply curve
If we make the assumption it's the only product made in an economy.
Likewise, in the case of demand in the micro economy, we consider demand as a single individual 's demand for an identical commodity, however in macroeconomics it is the totality of the demand for all goods and services by all customers in the economy.