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 London.JPG
Creation Date2011-05-25 20:59:28
File Size210,147 bytes (205.2 KB)
Dimensions1024 x 765 pixels
GPS Coordinates 51.50733, -0.12917