Adjustments, or manipulation as they're sometimes referred to is the minor movement of vertebrae in the spine. The objective of this movement is to realign vertebrae that have moved out of place for a number of reasons ranging from normal daily activity to trauma such as a car accident.
When these vertebrae are out of place, it has an overall systemic effect from muscular to the central nervous system. Without proper alignment and flow of all nerves and systems in the body from the brain, we can't function at our peak.
An adjustment is often a pressure from the chiropractor utilizing the hands or an instrument to move a vertebrae back into place. This happens with a quick movement and is often without discomfort. You may hear a noise that sounds like you're cracking your knuckles referred to as joint cavitation. It is the release of gases such as oxygen and nitrogen from the joint.
"Medicine is a collection of uncertain prescriptions, the results of which taken collectively, are more fatal than useful to mankind. Water, air and cleanliness are the chief articles in my pharmacopeia."