Shutter Speed.

Shutter Speed is a setting on the camera which controls the speed of the shutter.

changing the shutter speed effects the pictures greatly as a fast shutter speed would allow the photography to capture someone moving and freeze that motion in time on the other hand a slow shutter speed would allow the photographer to capture the movement for the duration that the shutter is open.

For example using a slow shutter speed would allow the photographer to have this effect;

(non of the following images are mine, see "'Painting with Light' 1,2, and 3 to see my examples.)

for example using a fast shutter speed to capture something within sports the photographer would be able to do this sort of effect;
(See "Freeze motion" for my examples.)