It is easier to explain what the Feldenkrais method is NOT than to describe what it is.
Its not strictly a therapy. Though a lesson can be therapeutic, resulting in a feeling of ease or relaxation, it is based on education rather than therapy or healing. The method aims for lasting change through education as opposed to a momentarily soothing massage.
Its not exercise. Feldenkrais considered exercise to be usually pointless and often painful repetition of bad habits where nothing is learnt. Feldenkrais was more interested in the intelligent body than in washboard stomachs or massive biceps. He did not advocate muscle for muscles sake.
In fact, Gaby Yaron who was one of Feldenkrais assistant cured herself after an accident, initially without moving a muscle. After she was hit by a bus (in her late 70s), breaking ribs and pelvis, all she could do was lie down. Nine months later she was teaching the Melbourne Feldenkrais Training programme how to do a headstand, by example. Simply by imagining each part of her body moving just as it should, with kinaesthetic sensing or thinking through, she cured herself. Many Feldenkrais lessons can be done in the imagination, or so gently that no effort is required.
Its not yoga either. Feldenkrais borrowed some wisdom from yoga but the premise of his method is entirely different, based as it is on ease. Anyone who has done a yoga class will know that ease is not yogas first principle.