Definition of Done
A formal, shared description of the quality standards an Increment must meet, used to create transparency about what 'complete' means.
What it means
The Definition of Done (DoD) is a commitment tied to the Increment. When a Product Backlog item does not meet it, it cannot be released or even presented at the Sprint Review as part of the Increment; it goes back to the Product Backlog.
If an organization has a shared DoD, all Scrum Teams follow it as a minimum, and individual teams may add stricter criteria for their own product. If no organizational standard exists, the Scrum Team defines its own, appropriate for the product.
Common mistakes
A typical DoD includes items such as code reviewed, automated tests passing, documentation updated, and deployed to a staging environment. It should get stricter over time as the team's engineering practices mature.
Example
The team's DoD requires unit tests, a passing build, and peer review before any item counts toward the Increment.