Grooming
In plain terms
Refining and prioritizing the backlog (backlog refinement).
Going deeper
Grooming (now called backlog refinement) reviews, clarifies, estimates, and reorders backlog items so they're ready for upcoming sprints. It keeps the backlog healthy.
Under the hood
An ongoing activity, not a single event; ensures top items meet the Definition of Ready.
Examples
Backlog refinement, estimation, clarification, prioritization, Scrum.
Think of it like...
Like tidying and prioritizing your to-do list so the next tasks are clear.