When you look at a post's edit history you can see each version of the question going back to the original version. Each version has a number next to it, starting with 1 for the original version. On the mobile app, the original version has an additional identifier next to the "1". It says "Initial Revision". As far as I can tell this label does not appear on the actual Stack Exchange sites.

Why would the original version be called "initial revision" if the original version was not a revision?

Here is an example from a recent question.

This is how the edit history appears on the site:

And this is how it appears on the mobile app:

The app screenshot is from version 1.6.6.2 if that makes a difference.