high pressure to areas of low pressure
As molecules are moved up to higher elevations there is less pressure being applied by their surroundings in the air of higher elevations.
to make it simpler think of it this way: if i am a runner i can run farther and faster at sea level because there is more oxygen and air molecule at the lower elevation than say a mountain top where the air is so thin.
So long story short pressure decreases with elevation because there are less outside molecules pushing against it in a finite space.
Another way to think of it is that all the molecules are resting at the bottom because they have weight(if minimal) that pulls them down like any other substance so they are packed closer together the lower the elevation is.
