Apple TV
What’s the difference between the app and the actual system that you have to purchase
Apple explains all of it's offerings for TV in www.apple.com/tv.
You will find they have a number of products including:
- Apple TV HD (hardware)
- Apple TV 4K (hardware)
- Apple TV App (app)
- Apple TV + (Apple's proprietary content)
- AirPlay
- Accessories
So I'd start on the web site and if you still need clarification on specific products please let us know.