The Exchangeable image file format, or EXIF, for digital photos has geotags which can be used to tell where a picture was taken. As noted in the Tip of the Night for May 27, 2016, you can easily view the precise longitude and latitude of a photo in Windows Explorer.
It's also possible to alter EXIF geotags with a free application called EXIF Pilot.
EXIF Pilot lets you review your photos in a file browser much like Windows Explorer. If you select a file, and then select 'Edit EXIF/IPTC/XMP' in the 'Edit EXIF/IPTC/XMP' menu, on the 'EXIF GPS' tab, you'll have the option to edit the longitude, latitude, altitude, and time stamp information for a file. In this example, I added coordinates to a file that I took with a camera set not to record geotags.
The file as edited lists coordinates of 29° 58′ 34″ N, 31° 7′ 58″ E.
. . . which is a place far, far away from Monument Valley.