Rescoring is the process in Agile Software Development where the Development Team often revisits the list of User Stories to review story point scores and move them up or down based on what the team had did in the past Iterations.
The main function of Rescoring is to fine-tune the Scope and Provide exact estimates on how long the team will take to work and to get finish the project within a iteration.
Further Reading:
https://searchsoftwarequality.techtarget.com/definition/rescoring