Apple Distribute App over Xcode Archive - App Store Connect vs TestFlight Internal only

I use Xcode in order to publish iOS App to Apple Store Connect in TestFlight- mode - it is my first publishing at Apple App Store Connect ever. I will do this by this tutorial:

Tutorial TestFlight

In this tutorial at 09:09 there has to be made a selection of distribution. My window looks like this:

So actually I don't really know if I should choose App Store Connect or TestFlight Internal Only. I would be thankful for any hint concerning that.

Both options will upload your binary build to TestFlight and be available to download in the TestFlight app. However, they are used for different purposes.

1. App Store Connect: this option is used when you want to upload and publish a new version. After this step, you can submit the build for review by tapping on the add build button, as seen below.

2. TestFlight Internal Only: this option will also ship your build to TestFlight. Your internal testing group on TestFlight will be notified as soon as it is published. However, you're unable to select the build as in 1. So, it's for internal testing only, before a release build.