Shutter speed allows you to do cool things; a long shutter speed allows you to take really cool photos like these:
And a short shutter speed allows you to take cool action photos.
A slower shutter speed makes the image darker, and a shorter shutter speed makes it lighter.
What I did for the above images is very simple. All you need is a tripod, a camera, and a flashlight, oh and a dark room (take the pictures at night). Set the shutter speed as long as possible then write whatever you want while pointing the flashlight at the camera. If you want to make separate words, cover the flashlight with your hand in between strokes. A slow shutter speed can also create a really cool star effect, and I hope to get some good pictures of that soon.