App Versioning is a new feature introduced in Joget v3.
It lets you manage the version of the application that you are developing, and lets you easily switch between and publish different versions even while in production.
It is a helpful tool for developers as it allows them to continue working/improving on an application while maintaining a production copy.
Users can, for instance, continue to use version 1 of a published application while developers work on an unpublished version 2.
Further reading: App Versioning and Publishing