Besides pressure, denoted in equations as P, gases have other measurable properties: temperature (T), volume (V) and number of particles, which is expressed in a mole number (n or mol).

Learn about gas pressure and how it is used in daily life in this KS3 Chemistry guide from BBC Bitesize.

The gas pressure variation in Earth's atmosphere is maintained by gravity. It's not proof there's a "container" of some kind around a flat Earth.