Rapport is that magical, mystical state where people have a real sense of connection. It is a state of openness and trust, a state of safety and security, a state of familiarity — and a state where someone is less critical of suggestions.
Building rapport is one of the most fundamental skills in NLP. Without it, little else works. With it, communication becomes effortless and change becomes possible.
See also: List 5 things to match to get rapport | What is cross over mirroring? | What is NLP?