Images taken by digital cameras contain both the optical information captured from the image sensor, as well as information about the image. This additional information is called metadata. This metadata often includes datum such as filename, capture date and time, the camera model and settings used, and geographic information if the camera supports it.
EXIF is short for Exchangeable image file format, and is a metadata specification for image and audio files, and is an area of the file that contains metadata information.
Photos taken with a device that has access to geolocation data can tag that information in the metadata of an image. Images that have this location data are referred to as “geotagged”.