Airplay

AirPlay capability is device dependent and system software dependent. You don’t need to install anything with Apple devices.

When you wish to use AirPlay, then from what device to what other device?

If you have an Apple TV box, then what model is it? Identify your Apple TV model - Apple Support

Would you like to use AirPlay from iPhone? Connect to Wi-Fi and start using in-app AirPlay controls, or Screen Mirroring from Control Center.

Would you like to use AirPlay to an Apple TV box? Turn on AirPlay in Settings.

Would you like to use AirPlay to a compatible third party device? Turn on AirPlay in Settings.

Use AirPlay to stream video or mirror the screen of your iPhone, iPad, or iPod touch - Apple Support

If screen mirroring or streaming isn't working on your AirPlay-compatible device - Apple Support

List of AirPlay 2-enabled smart TVs and third party streaming devices - Apple

AirPlay system requirements - Apple Support

Additionally there might be content/app restrictions. It does matter what you would like to stream. Content providers may not support AirPlay, or choose to block AirPlay, or have minimum system requirements for the receiving device. Sometimes AirPlay from a content provider app is supported, but not from their website.