Most digital cameras these days, including the consumer-level point and shoot models, offer manual modes to help you capture even better photographs.
There’s Shutter Priority (Tv) that makes it possible for you to capture sharp images of moving objects (like a racing car) while the Aperture Priority (Av) mode helps you alter the depth-of-field in a photograph. Finally, if you want control over both aperture and shutter speed, you go with the Manual Mode (M).
This Canon document explains Shutter and Aperture in pretty simple language:
A fast shutter speed will ‘freeze’ movement, giving a crisp, sharp image of the subject. A slow shutter speed can create deliberate blur in a moving subject – when photographing moving water, for example.
When you are shooting landscapes, you will often want everything from the foreground to the horizon to appear as sharp as possible. This requires a small aperture, such as f/16, to give a wide depth-of-field.
That’s all theory but if you really want to master the various manual modes on your digital camera, you got to go out and shoot.
Alternatively, you can use this online camera simulator – it’s a clever Flash-based tool where you adjust the various settings available in a standard digital camera and instantly see how they impact the final photograph.
You may alter the aperture, shutter, the ISO value or even the distance of the camera from the subject. A useful tool both for novice and amateur photographers. Thanks @Pogue.