What is a "Definition of Done"?

Here's my definition of the concept Definition of Done.

"A Solution has a User and a Provider. A User uses the Solution to reach an objective, while a Provider builds, maintains, and improves the Solution to support the User. However, both the User and Provider have needs before they can confidently interact with the Solution. Before a Provider releases a new Solution or an improvement to an existing one, a Definition of Done is a guide used by the Provider to ensure the Solution's User and any future Provider can begin or continue to use, build, maintain, or improve the Solution." - Shadow Smith

Definition of Done Diagram