Explain Atmospheric Pressure?

Answer 1

In what sense?
Its standard value at sea level? 101.325 kPa, 14.73 pounds per square inch

The reason why it exists? Air molecules are made of atoms and atoms have mass (very little per atom but it does add up). The total quantity of air on Earth pushes down on the ground (because of its weight): over each square meter of Earth's surface, there is a column that weighs 10.3 tonnes (= 10,300 kg = 101,325 Newtons).

A Pascal = 1 N/m^2, and a kiloPascal is 1000 Pascals.

101,325 N/m^2 = 101.325 kPa

Answer 2

atmospheric pressure is the pressure of all the molecules in the atmosphere pushing down on the surface of the earth its value can change daily and it's the reason the wind blows and why weather moves like it does