Use the built-in camera on Mac
Many Mac computers and displays have a built-in FaceTime or FaceTime HD camera located near the top edge of the screen. The camera automatically turns on when you open an app—such as FaceTime, Messages, or Photo Booth—or use a feature—such as Markup or head pointer—that can use the camera. You can decide which apps are allowed to use the camera on your Mac. See Control access to your camera.
Turn the camera on: On your Mac, open an app or turn on a feature that can use the camera. A green light beside the camera glows to indicate that the camera is on.
Turn the camera off: On your Mac, close or quit all apps or turn off all features that can use the camera. The green light beside the camera turns off, showing that the camera is off.