Thread:Project:Support desk/what does "deleted" mean in API:Deletedrevs?

hi, I've got a question about the API:Deletedrevs module as I couldn't find it in the help pages:

when exactly is a revision considered "deleted" and will be listed by this module? when all it's added chars are deleted by future revisions (detected via a DIFF) or if it was reverted during a rollback? or something else?