Shutter speed

Shutter speed is a common term used to discuss exposure time, the effective length of time a camera's shutter is open. shutter speed is the length of time that your image sensor ‘sees’ the scene you’re attempting to capture.
Shutter speed is measured in seconds – or in most cases fractions of seconds. The bigger the denominator the faster the speed (ie 1/1000 is much faster than 1/30).

Shutter Speed in isolation from the other two elements of the Exposure Triangle (aperture and ISO) is not really a good idea. As you change shutter speed you’ll need to change one or both of the other elements to compensate for it.

For example if you speed up your shutter speed one stop (for example from 1/125th to 1/250th) you’re effectively letting half as much light into your camera. To compensate for this you’ll probably need to increase your aperture one stop (for example from f16 to f11). The other alternative would be to choose a faster ISO rating (you might want to move from ISO 100 to ISO 400 for example).

Reference

Digital Photography School (2011) Introduction to Shutter Speed in Digital Photography. Available from: http://www.digital-photography-school.com/shutter-speed [date accessed: 10th October 2011]