why the pressure increases with the increase in depth?explain in detail

The deeper we decend into a fluid there is more weight above us to create pressure. So we say that pressure increases with depth.

Also mathematically, pressure difference between two points in a fluid is P₂ - P₁ = hg

If the lower point of pressure P₂ goes more downwards, h increases, thus increasing the pressure difference. This way also we say that pressure increases with depth h.