Note: macOS Sonoma or later on a Mac with Apple silicon, or macOS Sonoma or later on a Mac using Continuity Camera with iPhone 12 or later
Reactions fill your video frame with a 3D effect expressing how you feel. To show a reaction, make the appropriate hand gesture in view of the camera and away from your face. Hold the gesture until you see the effect.
To turn this feature on or off, select Reactions in the Video menu, which appears in the menu bar when a video call is in progress. To show a reaction without using a hand gesture, click the arrow next to Reactions in the menu, then click a reaction button in the submenu.
For more information about this feature, you can visit https://support.apple.com/en-us/HT212950