As you edit your application in the editor, it maintains a history of your changes. This is useful if you need to view or restore an earlier version of your application.
Every time you save your application in the editor, AppSheet saves away the current version in a Version History log. Sometimes these changes are ones you make explicitly. Other times the changes are made automatically by the system when it checks the consistency of your application.
As the creator/owner of an app, you can make changes to the app definition at any time. It's important to keep in mind your users as you update the app.
During the lifecycle of an app, you might occasionally want to work on a significant new version of the app. The new version may have very different data and a different user experience from the current version of the app. Clearly, you'd want to keep your users on your current version until the new version is ready for deployment, and then seamlessly swap them over. We call this an "App Upgrade" and here's how you can achieve this behavior (this is part of the Core pricing plan).
With updates and upgrades to your app, as well as viewing and restoring your data, you're able to adjust your app to changing needs.