ISO 1222 is a rulebook that tells camera makers how to put a little thing on the bottom of their cameras called a "tripod mount." A tripod mount is a small part of the camera that helps it stay still when someone wants to take a picture without holding the camera. When you take a picture while holding the camera in your hand, sometimes the picture can turn out blurry because your hand shakes a little bit. But when the camera is placed on a tripod, it stays very still and doesn't shake, so the picture turns out nice and clear. The rules in ISO 1222 help make sure that all cameras have the right kind of tripod mount, so that people can use any tripod they want with any camera.