Discoverer F.M. Alexander, was a Shakespearean orator who developed problems losing his voice. The problem occurred as soon as he tried to speak onstage, but he later observed the same response pattern in his common speaking style, to a lesser effect. Careful observation with multiple mirrors revealed that he needlessly stiffened his body in order to recite or speak.
His technique was based on successfully finding his way past his loss of voice, and putting his discoveries into practice on himself, as well as training teachers. Many Alexander teachers are of the opinion that using a vocal medium, emulating the founder, most rapidly accelerates the benefits of this discipline.
The Alexander technique is a way of learning how you can get rid of harmful tension in your body. Although certainly not a full definition of the Alexander Technique, this is a good start.
A more complete description is offered in Changing the Way You Work, The Alexander Technique.
The Alexander Technique is a method that works to change (movement) habits in our everyday activities. It is a simple and practical method for improving ease and freedom of movement, balance, support and coordination.
The technique teaches the use of the appropriate amount of effort for a particular activity, giving you more energy for all your activities. It is not a series of treatments or exercises, but rather a reeducation of the mind and body.
The Alexander Technique is a method which helps a person discovers a new balance in the body by releasing unnecessary tension. It can be applied to sitting, lying down, standing, walking, lifting, and other daily activities.
The Alexander Technique is an intelligent way to solve body problems. So begins an excellent article-length introduction to the Technique.