What does the Apple TV subscription include?

There is no subscription to the TV app.

It is a free application for congregating streaming video into one place.

AppleTV+ is Apple’s streaming service.

It only provides access to AppleTV+ shows and movies.

Apple Originals - Apple TV+ Press

If you order directly from Apple then Apple TV + the content as described in Apple TV+ - Apple that being said you should be more specific, there are some bundles available that include other apps including Apple TV+, you need to do your own research on that though to see what is available in your area.