Take a look at these super-cool photos that capture a type of light that the naked eye can't see. Infared phtography captures infared light - part of the electromagnetic spectrum (super-cool term) that's not visible to the human eye.
There are a few ways to snap these kinds of photos. One, you can completely convert your camera to shoot only infared - which can cost you up to 500 bucks and is irreversible. The second way is to use an infared filter. For $20+ you can experiment with this technique till your heart's content. Finally, you can use a photoshop filter, but hey, that's cheating.