Earth’s atmosphere is a relatively thin collection of gases. These gases are essential to life on Earth. As density decreases the further you get from the Earth’s surface, the atmospheric pressure also decreases.
The less density air has, the less air pressure there will be and the more density air has, the more pressure there will be. This pressure can change with altitude.
The density of gas particles is highest closer to the Earth’s surface and the pressure decreases as you get further from the Earth. Which means:
So, an object at sea level will have a higher atmospheric pressure than an object on top of a mountain. This is because there will be more particles around the object at sea level, so there will be more collisions with the sea level object than with the object on top of the mountain. If there are more collisions then there will be a greater force acting on the object.
By looking at the pressure equation:
We can see that, as long as the area means constant, increasing the force leads to an increase in pressure. This is why the higher force acting on the object at sea level leads to an increase in pressure.