Displacement map is the result of the converting the Unwrapped phase to Displacement, and that means the movement in your study area (LINE OF SIGHT)
Firstly Towards the Satellite and that means Uplift.
Secondly Away from the Satellite and that means Subsidence.
Put in your mind that The Line Of Sight (LOS) doesn’t mean Vertical movement.
Also I’d like to draw your attention to take a look at this topic