Adjustments, or manipulation as they're sometimes referred to, is the minor movement of vertebrae in the spine, or joint in an extremity (arm or leg). The objective of this movement is to restore motion and function to the restricted body part.
When these vertebrae or joints are "out of place" or restricted, 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 to move a vertebrae back into place...realign the spine. 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 hydrogen and nitrogen from the joint.
Overall, adjustments are an excellent way to keep the body functioning at its highest level. When the body is in alignment, the body is able to respond and perform to its best potential.