With the macOS Sequoia 15.2 beta, Apple has revamped AirPlay, adding new options for sharing a more limited amount of information on the screen when AirPlaying to an Apple TV.
There are now options to show your entire screen, a specific window or app, or your extended display. Limiting AirPlay to a specific app allows a presentation or photos to be shared on the larger screen of a TV without allowing viewers to see all of the content on a Mac.
In the current version of macOS, Apple allows for mirroring a Mac’s display to an Apple TV, but there is no option for sharing just a portion of a display.
Read more at MacRumors.com