What is demo content?

When a user activates a theme, they have an expectation of seeing their photos, theirs shop, their contributors and all of their content with a new style or twist. Themes provide this ability to showcase user content in different ways. How a theme gets that content is what we look for. When there is no content a theme should not show anything. This has been an issue in the past and this will hopefully add more information to that. Sounds simple, right?