Definition of Done
The Definition of Done (DoD) is a set of criteria for quality and completeness of the increment, against which the increment is evaluated.
DoD creates transparency and shared understanding of what work was completed as part of the Increment.
The Definition of Done is common across Product Backlog Items and consistent for a Product.
The DoD is established before the work begins and is expanded (as needed) over the period.
The Definition of Done is different from the Acceptance Criteria (AC). The AC is focused on functional scope of one PBI where as the DoD is focused on quality scope of the entire product.
See also: Increment, Acceptance Criteria