"Exchangeable image file format (officially Exif, according to JEIDA/JEITA/CIPA specifications) is a standard that specifies formats for images, sound, and ancillary tags used by digital cameras (including smartphones), scanners and other systems handling image and sound files recorded by digital cameras." as it says on Wiki.
Exif is part of most digital cameras file formats and on many cellphones will also record geotagging data obtained via GPS. Very useful if one can't quite remember where a photograph was taken!
In the Windows world, the basic File Explorer allows some Exif information to be revealed and various graphics packages also allow these data to be read. IrfanView is free and has a good Exif module that allows the images to be geolocated on a range of mapping systems, including, of course, Google maps.
ExifTool from Phil Harvey provides an OpenSource tool kit which can be used via the CLI or a GUI. This software also forms the core to the elegant PicaGeoTag which which allows image Exif to be read & written as well as located on a map.
Faststone image viewer is also worth looking at, as it manages image manipulation as well as Exif plotting.