The shutter keeps light out of the camera except during an exposure, when it opens to let light strike the image sensor. In respect to just exposure, faster shutter speeds let less strike the image sensor so the image is darker. Slower speeds let in more so it's lighter.
As the shutter speed gets slower, the image gets lighter. The reason you don't usually see this effect in your images is because when you or As the shutter speed gets slower, the image gets lighter. The reason you don't usually see this effect in your images is because when you or the camera change the shutter speed, the camera changes the aperture to keep the exposure constant.camera change the shutter speed, the camera changes the aperture to keep the exposure constant.
In addition to controlling exposure, the shutter speed is the most important control you have over how motion is captured in a photograph. The longer the shutter is open, the more a moving subject will be blurred in the picture. Also, the longer it's open the more likely you are to cause blur by moving the camera slightly. Although you normally want to avoid blur in your images there are times when you may want to use it creatively.
A fast shutter speed opens and closes the shutter so quickly a moving subject doesn't move very far during the exposure. A slow speed can allow moving objects to move sufficiently to blur their image on the image sensor