Question

Why is there a variation in distribution of pressure in atmosphere?

Answer 1

I suggest you rephrase the sentence in this way:
Without variation in atmospheric pressure at different locations, there would be no wind.

Higher pressure will push the air to flow to places where lower pressure dominates, just like you squeeze the toothpaste out of its container (perhaps this example is not very ideal, but still vivid).

That is, a force is imposed on the ensemble of air molecules therefore driving them into motion. The direction of the force inflicted by the difference in pressure distribution is the direction of the gradient of pressure distribution.

This opinion is a very classical explanation for the formation of the wind.

Answer 2

Answer:

the density and pressure in air decreases with altitude