Geotagging is the act of adding information about where someone or something is to a digital photograph, video, message, or similar file. The extra information is usually a place on the earth — often GPS numbers, sometimes a place name. Phones do this a lot: a picture of a night market may quietly carry the street as well as the image. People geotag posts on purpose so friends can find the café, or a phone may do it in the background unless you turn that off. It is an internet-and-phone word, informal in talk, a little more technical in settings menus. Though actually the tag can be wrong, old, or copied from somewhere else, so 'this file has a geotag' is not the same as 'this really happened at that spot.' The ability is the point of the word: you can pin a place to the file.