A digital camera holds valuable information that you may not be aware
of. It's called Exif, meaning "Exchangeable image file format, a
specification for the image file metadata format used in audio and
image files".

Now that you have that memorized, :), in real English it means the
info. that is stored in each digital image. Depending on the editing
program you use, you can see just a few items or up to 50 or 60, many
of which I don't understand.

Accessing the Exif differs depending on your program, but usually if
you right click an image you can see the date and time it was
created. To see the full Exif in some programs you need to open the
IMAGE menu or VIEW menu and click PROPERTIES or INFORMATION.

I use Irfanview, a free program. In an image I just checked I saw 59
entries in the Exif.

One way I like to use the Exif is for time study. In this example we
can see how quickly a van fire was put out. Open the first image
(upper left), then click NEXT on the right side above or below the
image to advance to the next one. Each image except the last shows
the exact time, taken from the Exif. It is easy to see that from
pulling the booster to initial extinguishment was just 11 seconds.
That included a quick sweep up the tree that was igniting.

http://www.pbase.com/dickh/van_fire_time_study