Before you begin reading this post, be sure and click on the previous post that explains the elements that go into the EXPOSURE TRIANGLE. The post is called The Mystery of Manual Photography. It covers aperture, shutter speed, and ISO. This will help you understand and apply the exposure triangle theory.
To understand exposure it is important to understand “The Exposure Triangle” and how ISO, shutter speed and aperture come together to effect each other. In order to maintain the “correct” exposure, any change in one element needs to be compensated with an opposite change in one of the other elements. By adjusting the shutter speed we can better freeze or express movement. By adjusting aperture we have play with depth of field thereby either highlighting a small element of our subject or expressing the grandness of our subject. But in doing so, we now know how to get back to that “correct” exposure! Once you start understanding exposure in this way you are well on your way to increasing your photography skills.