What is called atmospheric pressure, what is the reason for its existence.

Atmospheric pressure is a force directed towards the center of the Earth, which is exerted by the mass of a column of air in the atmosphere per unit area of objects. It is due to the gravity of the Earth, when all bodies have mass, including air, which presses on all other bodies. The air itself is of very low density, but due to the fact that the Earth’s atmosphere extends for many tens and even hundreds of kilometers, the height of the pressing air column turns out to be large, and it has an impressive mass.