RTC: Criteria of Acceptance and Test conversation relation

The 'Criteria of Acceptance' in agile templates are usually a description of what criteria need to be fulfilled to accept a story as implemented. These criteria are typically described before the story gets implemented. It just provides with criteria that allow to say work is done. This is important, because otherwise you can never say work is done, because there is typically always something in addition that could be asked for.

I am not sure what a Test conversation is.