Following up on the different types of IDs from last time, it’s often useful to have an ID that can be sent in a URL. The unique ID may not be appropriate for many reasons.
Many systems use something called a slug for this purpose. A slug must be unique, but can change under some circumstances. It should be easier for a human to work with than the raw ID.
None of what I’ve described covers different revisions of the data, needed for historical diffs.
Update: approach different IDs for different uses.