The telephoto lens on an iPhone is a camera lens that allows for optical zoom, which offers superior image quality compared to digital zoom. It is one of the three rear-facing lenses on the iPhone 11 Pro and iPhone 12 Pro models, along with the wide and ultra-wide lenses. The telephoto lens is designed to zero in on distant subjects and is the equivalent of a zoom lens on a DSLR camera, enabling you to get up close and personal with your subjects without physically moving closer. It is ideal for taking portrait mode shots and zooming in and out to get your desired image. The telephoto lens gives you an "optical zoom" that lets you take photos at different distances that look just as natural as those without zoom. The telephoto lens is not available on the iPhone 11 and iPhone SE 2 models. To use the telephoto lens on an iPhone, you can switch between the different camera lenses on your iPhone by tapping on the 0.5x, 1x, and 2x buttons in the Camera app.