NLP is the use of several subtle strategies to communicate to the subconscious mind
of others in order to influence them to do something without them knowing it. NLP (Neuro Linguistic Programming) is a special type of hypnosis that occurs in a conversation, the person listening does not know that he is being hypnotized and so this removes the barrier.
The model was actually created by John Grinder and Richard Bandler who studied and modeled Milton's approach over a period of time in 1975-76 and published to volumes which finally brought about the current model of NLP.
This will naturally bring some restriction as not everyone will succumb to the idea of being hypnotized. The fact is that while though the person does not know that he is under an hypnotic influence he shows the signs of some being hypnotized, which the hypnotist take advantage of.
Another advantage it has is that it deals directly with the subconscious mind. So the person you are dealing with is not aware of what you are doing. Naturally the conscious mind controls the subconscious mind but the subconscious mind has a way it controls the subconscious.
You also learn to get people into action. Because you have control over the conversation, you also have the ability to get people do your bidding. There are several ways to do that and all these can be learned from its techniques.
NLP can also teach you the model that will enable you to close any sale. You know what to look for in any prospect you determine their weakness and then can manipulate that for your profit.
Lastly the techniques you learn from the art will help you to persuade people to follow your course.
NLP is indeed very important. It is usually advised that you research very well before you purchase a program.