Shareplay is the feature that allows you to share your screen in Facetime. It is a new feature introduced in iOS 15 and macOS Monterey that lets you watch, listen, and play together with your friends and family over FaceTime. You can share your screen to show apps, webpages, photos, and more, while seeing and hearing the reactions of others on the call. You can also stream online content from supported apps, such as Apple TV, Disney+, and Spotify, and control the playback and volume for everyone. Shareplay works across iPhone, iPad, Mac, and Apple TV, and you can join or leave the session at any time. To use Shareplay, you need to have a device that meets the minimum system requirements, an Apple ID, and a Wi-Fi or cellular connection. References: SharePlay - Apple, Share your screen in FaceTime on your iPhone or iPad - Apple Support