One of the nerdy cool things about files is the metadata (data about data) that they contain. For music files, the metadata often contains the artist and song names. For text files, the metadata can contain information about the type of encoding. For image files, the metadata often contains information that can tell us what digital camera was used to take the photo, and even what software was used to modify the photo afterwards.
I accidentally drag-dropped an image onto my text editor window and was reminded of the wonders of metadata.
Although most of the file, when viewed in a text editor, is not human-readable, we can still see some interesting information that we would never see or know about by just opening the picture in an image viewer.
We can see that the photo was taken using a Nikon D300. We can also see that the image was modified using the Paint.NET software as well as some manner of Adobe software. Although there exists specialized software to extract more information from the metadata of media files, such as dimensions and bit-depth, hardly anyone wants to install that stuff on their computer.
So the next time your friend or colleague sends you the latest pictures they took with their digital camera, be sure to freak them out by referencing the exact model of camera they used to take the photos.