The Version Tab is where you can deploy your plugin and push updates, bug fixes and other improvements.
A plugin can be published on an open source license (MIT) or a private license. The open source license will make the plugin free on the plugins marketplace and other users may copy the code. Note that once a plugin has been published as Open Source, you won't be able to take it back to private.
When a plugin version is set to private, you can authorize some apps to have access to this plugin. Note that this is a different concept from the test application you use to test your plugin. These apps will be able to use the plugin in production.
When you clone an app that has access to a private plugin, Bubble does not remove the plugin from the newly created app to prevent the app from breaking. If you want to withdraw the plugin from the copy of the original app, you should delete it in the Plugins Tab of the app.
When you deploy your plugin, or push a change, you can define the change type and define a caption for the deployment. Deploying will generate a version number and will prompt users that have installed your plugin to upgrade their plugin in their app.