When a developer says a story is done then what it means? Coding is done, coding with unit testing is done? Testing also done? accepted? It is quite confusing if each developer in the team have thier own understanding of "done". We can't proceed and have status updates efficiently without having a common understanding and definition of done.
So, idea is your project, your team and you together should together agree upon definition of done. How precisely and accurately you want this to be defined? Team has to have list of criteria need to be satisfied to call out a story as DONE.
It is necessary for team to know that if laid our requirements for "done" at not met for the story at the end of sprint means story points can't be claimed and it affects velocity.
Example of definition of "done" is -
Coded to standards, unit tests written, reviewed, tested, integrated and documented.
Some teams can add additional steps, say "Running Automation tests" to definition of done if that applies to their project.