Shutter speed is the amount of time a cameras shutter is held open. The normal reason for adjusting shutter speed is to compensate for various levels of light. Generally it is preferable to have a higher shutter speed, but in lower levels of light, it is not always possible.
Common shutter speeds are 1/500, 1/250, 1/125, and 1/60 of a second. If the shutter is held open for longer than 1/60 of a second, it can be difficult to avoid blurring. With a great enough aperture (shutter opening) and enough light, shutter speed can be increased to 1/2000 second or greater to significantly reduce blurring. This high-speed method is ideal for photographing or recording objects in motion.