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 Monaco.JPG
Creation Date2011-05-29 14:53:14
File Size268,384 bytes (262.1 KB)
Dimensions1024 x 765 pixels
GPS Coordinates 43.74017, 7.43