What Is Shutter speed?
Light passes through the camera’s lens, but is only allowed to reach the film or sensor when a mechanical curtain, called the shutter, is opened by pressing the shutter button. The length of time that the shutter is open is called the shutter speed, and it is expressed as a fraction of a second.
A fast shutter speed, like 1/2000 of a second, will stop motion in an image. A long shutter speed of several seconds could be used to reveal the motion of a flowing river, or other dynamic subjects. Shutter speed is one of the three pillars of exposure, along with ISO and aperture. It gives us incredible creative control and the ability to convey motion, even in a single image. In automatic exposure modes the camera will select a shutter speed for you, in shutter speed priority mode (TV), the photographer selects the best shutter speed for the subject, and the camera calculates the correct aperture for a properly exposed image.
I highly recommend reading our in-depth beginners article about understanding shutter speed.