Neuro-Linguistic Programming (NLP) is defined as the study of the structure of subjective experience and what can be calculated from that and is predicated upon the belief that all behavior has structure. People such as Virginia Satir, Milton Erickson and Fritz Perls had amazing results with their clients. They were some of the people who’s linguistic and behavioral patterns Richard Bandler built formal models of. He then applied these models to his work.
Because these models are formal they also allow for prediction and calculation. Patterns that may not have been available in any of these people’s work could be calculated from the formal representations he had created. New techniques and models were (and still are being) developed.
Since the models that constitute NLP describe how the human brain functions they are used in order to teach them. NLP is not a diagnostic tool. It can only be applied and can therefore only be taught experientially.