Aggregate supply (AS) is the total amount of goods and services that firms produce and supply in an economy at a given price level in a given period of time. It is the amount of goods and services that the firms will produce, depending on the level of aggregate demand and the ability of the firms to respond.

Aggregate supply is a key component of macroeconomics and is used to help determine economic performance, depending on the market environment. Aggregate supply is affected by the cost of production, the total labor force, the price and availability of inputs, prices of substitute goods, and the degree of competition in the market.

The aggregate supply curve depicts the relationship between overall price level and output. It slopes upward because of the law of diminishing returns. As price level increases, firms supply more products, but the extra output becomes harder to obtain as the costs of inputs rise. As a consequence, the aggregate supply curve will become steeper as the amount of labor and capital rises.

The aggregate supply curve can be divided into three distinct sections. The first is the Keynesian range, which is when an economy is producing goods and services well below its long-term capacity. The second is the intermediate range, which is when the economy is capable of producing goods and services at its long-term potential. The last section is the classical range, when the economy is producing goods and services at or above its long-term capacity.

Government can influence the level of aggregate supply by changing the tax rates, the monetary policy, and the degree of regulation. Lower taxes and an easier monetary policy may provide incentives to firms to increase the amount of goods produced or services delivered. Increased regulation, on the other hand, could lead to a decrease in the supply of goods and services. Government spending can also act as a short-term stimulant to the economy, providing a boost to the aggregate supply of goods and services.

In general, an increase in aggregate supply is viewed as beneficial for an economy, as it leads to increased output and more employment opportunities. On the other hand, a decrease in aggregate supply is usually seen as detrimental, as it can lead to a decrease in production and employment.

Overall, aggregate supply is an important factor in the macroeconomic health of an economy. Knowing the amount of goods that firms are producing and the level of inputs needed to produce these goods and services can help economists and government officials make informed decisions on how to structure economic policy to maximize output in the long run.