Chiropractic [1] aims to aid the human body's own innate intelligence, which seeks balance, or homeostasis, among systems in the body. Chiropractic also emphasizes that proper structure is necessary for proper function and holds that the nervous system is the primary coordinator of function throughout the body.
As
described by chiropractic founder Daniel David Palmer, the human body
is a dynamic self-regulator. It seeks to maintain "homeostasis," which
is a state of balance among all the systems needed for the body to
function correctly. Homeostasis is one of the fundamental
characteristics of all living things.

Chiropractic theorizes that nerve and organ dysfunction is often the
result of misaligned vertebrae of the spine. When the vertebral
segments become injured, fixated, or malaligned, soft tissues become
irritated, adjacent muscles often tighten, and nerves can be irritated
and their function impaired. This is called an "intervertebral
subluxation."
This very common condition results from trauma, postural stress, congenital abnormalities, disc degeneration, and the toxic effects of infection. Simple daily living puts everyone at risk for this quite common condition.
Chiropractors use spinal assessment and adjustment to reduce the subluxation, and thus alleviate irritation of the nerves. Because the spine is such a complex structure, adjustments often involve multiple levels of the spine and even the extremities. The goal is balance and normalcy, and the cause of the stress may lie at a distance from any point of discomfort.
Leach, A. (Ed.). (2004). The chiropractic theories: A textbook of scientific research (4th ed.). Philadelphia, PA: Lippincott Williams & Wilkins.
Haldeman, S., Chapman-Smith, D and Peterson, D.M. (Eds.). (1993). Guidelines for chiropractic quality assurance and practice parameters: Proceedings of a consensus conference commissioned by the Congress of Chiropractic State Associations. Gaithersburg, MD: Aspen Publishers.
Haldeman, S., Dagenais, S., and Budgel, B. (Eds.). (2005). Principles and practice of chiropractic. New York, NY: McGraw-Hill, Medical Pub. Division.
Links:
[1] http://www.takingcharge.csh.umn.edu/glossary/3#term12
[2] http://www.takingcharge.csh.umn.edu/create-healthy-lifestyle/diet-nutrition
[3] http://www.takingcharge.csh.umn.edu/our-experts/larry-kuusisto-phd-dc
[4] http://www.takingcharge.csh.umn.edu/explore-healing-practices/food-medicine
[5] http://www.takingcharge.csh.umn.edu/activities/baby-ear-infections-high-bandwidth
[6] http://www.takingcharge.csh.umn.edu/activities/man-neck-pain-headaches-high-bandwidth
[7] http://www.takingcharge.csh.umn.edu/activities/woman-gets-spine-adjustment-high-bandwidth