Backlog Refinement
Backlog refinement is a regular event typically conducted one or more times during a typical iteration, encompassing a variety of activities to ensure that the team's upcoming backlog is well-organized and prepared for action.
During this event, the team undertakes several tasks, including incorporating user feedback through the addition, update, or removal of stories. They also estimate the effort required, prioritize based on importance, identify dependencies between different items, and ensure a proper rebalancing of capacity of upcoming iterations if necessary.
Resources
The topic of Backlog Refinement is covered in the Adaptive Agility Fundamentals class.
This Scrum Alliance article talks about Backlog Refinement in details -- what it is, what it is not, and how to do it, etc.