How Done is done?

The most important thing in Scrum is to get a working releasable increment every sprint, but How done is your done?

can Product Owner really release the software if he and she feel like it? Have you done all your testings, including unit testing, automatic testing, integration testing and more? Have you written your release notes? If that is a mobile app, has all the updated screen shots prepared? Quite often there are something missing to stop you from releasing the software immediately. That gap is quite often, a good starting point to measure your technical debt and your engineering practices