Shutter speed is how quickly the shutter opens and closes. When the shutter speed is on for long more light gets into the camera so when it is on for a short time less light gets into the camera. If you have a short shutter speed time if you want to capture movement then you will get a still picture so you could take a photo of fast moving things such as animals or bullets being shot. However when you have a longer shutter speed time and you try to capture movement the picture will be blurred this is good to show movement or speed.
Fast |
Medium |
Slow |