Different people in the NLP community understand modeling in different ways.
I had the good fortune of learning from wizard John Grinder early on in my journey.
(Incidentally, it helped me understand a key factor that distinguishes Tony Robbins from so many other NLP Practitioners — he was taught by John).
Here is a bit from his masterpiece "Whispering In The Wind," which he co-authored with Carmen Bostic St Clair, in which he explicitly defines NLP and describes the core activity of the field:
NLP is a modeling technology whose specific subject matter is the set of differences that make the difference between the performance of geniuses and that of average performers in the same field or activity. In this sense, the objective of modeling studies in NLP is to explicate in a transferable and learnable code these sets of differences. The core activity, then, is the mapping of tacit knowledge onto an explicit model.
Notice how he explicitly states what NLP is: a modeling technology.
Not a therapeutic modality. Not a self-improvement method.
Notice he states the subject matter of the field: the set of differences that make the difference between the performance of geniuses and that of average performers in the same field or activity.
Not language patterns. Nothing hypnosis-related. Not getting others to do what you want. Not rapport.
Notice he states the core activity of the field: the mapping of tacit knowledge onto an explicit model.
I'm bringing this to your attention because if you look at the curriculum of most Practitioner courses, you'll notice they are far removed from this understanding of the field.