A product backlog is the single, prioritized list of everything that might be built for a product — features, fixes, improvements, and technical work. It's ordered by priority, so the most important items sit at the top. The backlog is the team's source of truth for what comes next.
What a backlog contains
TOP → well-defined, ready to work on soon (small, clear, estimated)
MIDDLE → roughly defined, needs more detail before starting
BOTTOM → vague ideas and "maybe someday" items (low detail is fine)
Detail decreases as you go down. It's wasteful to fully specify items you may never build.
Backlog refinement (grooming)
is the ongoing activity of keeping the backlog healthy: clarifying items, adding acceptance criteria, splitting big items, estimating, and re-prioritizing.
