What does a shutterer do?

Answer 1

Simply, the shutter release takes the picture. The shutter release is the button on a camera which, when pressed, "releases" the spring tension on the shutter which "trips" the shutter to open and close and expose the film or sensor to light coming through the lens.

But I wondered if you were actually asking what a cable release does. Most film cameras and some digital cameras have a little threaded port, usually on the shutter release button, into which you can screw a cable release, which is a flexible cable with a spring loaded plunger which when depressed will release or trip the shutter. The flex in the cable allows the shutter to be tripped without moving the camera.

A cable release is used when the camera is solidly mounted on something such as a tripod and allows the photographer to release the shutter without directly touching the camera. This is important when the exposure is long (some photographers prefer to use a tripod and cable release for all exposures, but others consider a "long" exposure to be any shutter speed equal to or longer than the focal length of the lens in use) and "time" exposures running to several seconds or even minutes. The cable release allows the shutter to be held open for long periods without the danger of even slightly moving the camera and blurring the exposure. Some cable releases are equipped with locking devices so the photographer doesn't have to hold the plunger down for several minutes.