The backlog is the list of all the work that needs to be done to deliver the project.
A backlog in OnTheSamePage can be grouped in to themes, to help with navigation and understanding for when your backlog gets really big. Search and filter capabilities give you the opportunity to refine the view of the backlog to reflect what you want to see. And custom fields let you add your own data elements on to the backlog.
The AI watches your backlog and helps you along the way. If you've got two stories that look like they're the same thing, the AI system will tell you. If you don't have enough of your backlog refined, the AI system will tell you. If your backlog hasn't been prioritised recently but has had a lot of new stories added - the ai system will tell you. Thank you AI system.