sorry for making it vague.can u please tell me if i m wrong anywhere in my thought process? let's consider a conductor which has charges distributed on it. now due to these charges there is an electric field present on the exterior part of the conductor. let there be another test charge which is progressing towards it. as its progressing its potential energy difference is increasing. the reason being the force against which its moving is also increasing. when its on the surface of the conductor it becomes maximum. the moment it enters the conductor it doesn't increase neither decrease. we know that electric potential is the diffrence of potential energy between two points divided by the charge. in my case consider that one point is on infinity and the other is inside the conductor. we can clearly see that the difference doesn't change once the charge is inside the conductor so the potential doesn't change. therefore its constant.