Shutter speed is the measurement of how long the shutter of your digital camera is open during the time you snap an image. Shutter speeds are measured in seconds and fractions of seconds; the larger the bottom denominator is, the faster, the shutter speed will be. An average snapshot will have a shutter speed at around 1/60th of a second, anything longer than that should be accompanied by a tripod to eliminate shake in the image.
Often, you can hear the sound of your shutter opening and closing when you press the shutter release button.
Uses of a low shutter speed (1 - 1/60)
Uses of a fast shutter speed (1/60 – 1/500)