What effect does aperture and shutter speed have on exposure?

Shutter speed controls how long the sensor/film is exposed. Shorter shutter speeds normally provide a sharper image. Longer shutter speeds give you more blur.

If you're hand holding your camera a good rule to go by is to multiply you focal length by two and use that as your shutter speed. For example, if your focal length is 100mm--your shutter speed should be 1/200sec or faster.