Sorry, as others have said, I meant a text log or "history". Basically, the ability to view the last N lines of text. For some VNs, this log also allows you to replay the voice lines, to jump back to specific lines/scenes, and even to bookmark specific lines, separately from saving the game. Ren'py is actually a bit unusual in this regard, since the default behavior is a rewind feature rather than a text log. However, most commercial Ren'py VNs will show the history as a log.
I think they meant scrollback. as conventionally a backlog would evoke "work yet to be done", whereas in this context we're talking about a conversation history one can revisit.
Like you can either read a log of what characters said in a scene so far, or simply go backwards through the story to reach an earlier line and view it again.
