Film-based cameras must have a mechanical shutter. Once you expose film to light, it can't be wiped clean to start again. Therefore, it must be protected from unwanted light. But the sensor in a digital camera can be reset electronically and used over and over again. This is called a digital shutter.
Some digital cameras employ a combination of electrical and mechanical shutters.
Exposing the Sensor These two aspects of a camera, aperture and shutter speed, work together to capture the proper amount of light needed to make a good image. In photographic terms, they set the exposure of the sensor. Some digital cameras also offer the ability to adjust the aperture settings by using menu options on the LCD panel. More advanced hobbyists and professionals like to have control over the aperture and shutter speed selections because it gives them more creative control over the final image. As you climb into the upper levels of consumer cameras and the realm of professional cameras, you will be rewarded with controls that have the look, feel and function common to film-based cameras.