What is the difference between maida and aata ( wheat )?

We get maida (flour) from wheat after the outer layer is removed. Atta is whole wheat flour.

The outer brownish layer is removed from the wheat and the inner white portion is used to make maida flour.

That is the reason whole wheat flour(includes the brown outer layer) is considered healthier than maida flour as it contains fiber which maida flour is missing.

Maida is a refined product of wheat - meaning it is obtained after processing the wheat, which makes it less nutritious. The less a grain or vegetable is processed, the more nutrients it retains.