Question

What is the difference between Altitude pressure and Atmospheric pressure?

Answer 1

see below

Explanation:

pressure is due to the weight force of the air column that is upon a square meter of surface. Its value is about `1 atm = 1,033 kg/(cm^2) = 101325 N/m^2` al the sea level
Of course if you go upward the value of the pressure decreases because decreases the heigth of the column of air.

unfortunately this decrease is not linear because also the density of air decreases with heigthness.

You can think it is linear for the first 1000 m, while after 5500 m its value is near the half compared with the pressure of the sea level.
Atmosferic Pressure is also conditioned by the meteriological weather and by the moisture because steam weighs less then dry air