The dynamic range of an image is its full range of brightness from dark to light. The iPhone camera can balance the shadows with highlights to create a more dynamic image.
HDR photography is great for when your shot features the sky, or if an individual or object is heavily backlit, or if the sun is shining directly onto the subject.
To use the HDR function, open the Camera app, tap HDR along the top menu bar, then choose whether you want to have HDR applied automatically or manually keep it on or off at all times. You’ll notice the difference right away!