Positioning is how you differentiate yourself in the mind of your prospect. It’s also a body of work on how the mind works in the process of communication.
Repositioning is how you adjust perceptions, whether those perceptions are about you or about your competition.
In both cases, in order for your strategy to work, you must understand how the mind works or how people think.
Jack Trout, Repositioning – Marketing in an Era of Competition, Change, and Crisis, P10.