Nowadays every photo taken with a mobile phone or digital camera contains metadata. This metadata, called Exif data, contains information about your camera, like brand and model name, the dimensions of the image and - when available - also GPS coordinates which reveal the location where the picture was taken.
File NameExample St Louis.jpg
Creation Date2012-05-28 13:35:47
File Size155,220 bytes (151.6 KB)
Dimensions1024 x 1365 pixels
GPS Coordinates 38.6255, -90.18333