The product backlog is considered the backbone of iteration planning. Within the backlog all work items should be included, for example:
- user stories
- changes in design
- customer requests
- technical debt
- action items gained from retrospective meetings and so on
Including large amounts of information in the backlog ensures that all team member's work items are included in the overall planning for each iteration. Team members can then discuss with the product owner before starting each iteration with extensive knowledge regarding the work that needs to be done.