NLP or Neuro Linguistic Programming is the study of pattern of excellence and using tools and techniques to eliminate bad habits and demonstrate peak performance.
Hypnosis is about entering into a trance state and using suggestions to work with our unconscious mind.
But why people always bring these two fields of discipline together? This is because NLP is the study of pattern of excellence found in experts in the various fields and disciplines. And a reasonable chunk of NLP studies is based on the study of Milton Erickson, a renowned hypnotherapist. It is later developed into Milton Model in NLP.