Learn in the textbookComponents of Scrum
DefinitionThe Product Backlog (プロダクトバックログ) is a list, ordered by value from highest down, of what is needed to improve the product.
ExplanationNew features, improvements and bug fixes are lined up as items, and the higher an item sits, the more detail it is given. The Product Owner is accountable for its content and order and keeps adding and reordering items as circumstances change, so it is never a list made once and finished.
AnalogyIt is like a shopping wish list: you add things whenever they come to mind and keep reordering so that what you need most right now sits at the top.
Memory hookIn everyday English, a backlog is a pile of work not yet done. Think of it as the ledger that holds the work still to be taken up.