NLP, or "Neuro Linguistic Programming," is the art and science of modeling, which is the process of duplicating excellent behavior.
NLP aside from being the most effective brief therapeutic application, is the methodology that studies what a person does inside their head (language, filters, programs, learning styles, the way in which people experience and interpret the world, etc.) and such excellent behavior can be duplicated to produce the desired results or behavior changes a client is seeking to gain.
NLP was originally created by Richard Bandler and John Grinder. They began modeling and duplicating the excellent behavior of some communicators and therapists such as Hypnotherapist Milton Erickson, Gestalt therapist Fritz Perls and family therapist Virginia Satir.
Today, NLP is widely used in business to improve management, sales and achievement/performance, inter-personal skills; in education to better understand learning styles, develop rapport with students and parents and to aid in motivation; and of course, NLP is a magnificent set of therapeutic tools for personal development.