When you take a digital picture, the camera attaches all sorts of data to that image. Most camera users are familiar with the basic data -- date, time, file name, etc.
But there is a lot more information a camera can put in the picture. That inlcudes things like exposure time, ISO settings, zoom, flash, white balance, camera serial number, number of times the camera has been used, and so much more.
By understanding those settings, you can learn more about your pictures, your camera, and your skills as a photographer. Some of it may also be useful in photo editing.
This data is called EXIF data. Sometimes it's difficult to access without the right software.
I'm currently playing around with PhotoMe, which is a free, downloadable tool that will show you all the EXIF data on a picture. You can download a copy here, and start playing with it.
How much data is in this photo?
Click here to see the EXIF data from PhoteMe