air pressure or atmospheric pressure is referred to the force exerted on a particular surface by air present above due to the gravitational pull of the earth.
Explanation:
in simple terms -air has weight and it constantly exerts pressure against everything in the surrounding. This pressure uses gravitational pull of the earth to exert its force on or over a surface. This is called atmospheric or air pressure. It can be measured by using barometer. The unit of measurement is atm (atmosphere)
