It is very inconvenient for MacBook users to take photos. On Windows, there is the Camera app which can be really useful at times.
How can I use my Mac to take pictures?
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There's always Photo Booth.app. I guess it's always going to be a bit awkward to use a laptop as a camera for pictures of anything other than the user.
The question is vague but you might be looking for SecuritySpy and the built-in camera is among the supported ones.
SecuritySpy is an NVR (Network Video Recording) software that lets you turn your built-in camera (among a larger number of supported cameras) into a useful video surveillance system as it feature smart motion detection. Thus letting you put your built-in camera to good use, like taking a video or screenshots when it detects movement.