Everything a phone does depends on some app or other.

Apps are the devil.

It is an option when you use the camera that determines whether a single image is captured or a short sequence of images. If you capture the sequence, you can later select a single frame from it with Edit. I find it very helpful when trying to capture subjects that are moving like small children.

When using the camera, the option is a round icon at the top center somewhat like ripples in a pond.