Neurolinguistic Programming is the science of changing our actions and behaviour by changing the language of our thoughts. It studies our thoughts and the way we process them (neurology), the language we use to express ourselves (linguistics), and our behaviour patterns (programming), to understand how their interaction is either helpful or detrimental to our deepest goals and desires.
There are several excellent resources if one wants to further understand how this process works. NLP was developed by Richard Bandler and John Grinder, and both their sites are storehouses of information. I also recommend anything by Tony Robbins as well.