An AppleTV is a device that enables you to connect your computer to your projector, wirelessly. No Cables Needed!
It is also a device that has its own set of 'apps' that you can use to play content, without the need for your computer. Eg: A YouTube video.
The Remote Control
TvOS (AppleTV Operating System)
AirPlay
Learn how to find menus, play content, and more.
Use Screen Mirroring to see the entire screen of your iOS device on your Apple TV or AirPlay 2-compatible smart TV.
Connect your iOS device to the same Wi-Fi network as your Apple TV or AirPlay 2-compatible smart TV.
On iPhone X or later or iPad with iOS 12 or later: Swipe down from the upper-right corner of the screen.
On iPhone 8 or earlier or iOS 11 or earlier: Swipe up from the bottom edge of any screen.
Tap Screen Mirroring.
Select your Apple TV or AirPlay 2-compatible smart TV from the list. Need help?
If an AirPlay passcode appears on your TV screen, enter the passcode on your iOS device.
Your TV uses your iOS device's screen orientation and aspect ratio. To fill your TV screen with the mirrored iOS device screen, change your TV's aspect ratio or zoom settings.
To stop mirroring your iOS device, open Control Center, tap Screen Mirroring, then tap Stop Mirroring. Or press the Menu button on your Apple TV Remote.