NLP is the term for a huge number of techniques put together by John Grindler and Richard Bandler. They watched various successful psychotherapists and psychologists and took the processes that were most effective.
NLP stands for Neuro Linguistic Programming. We are programmed by the way in which we view external events and internalise them through our 5 senses. How we internalise and interpret external events in our mind is what programmes our behaviour. We can change how we interpret and view external events and so change our behaviour.