The map is not the territory

An abstraction derived from something, or a reaction to it, is not the thing itself.

I bet you will read that sentence again. Anyway, let me explain.

What you see below is not a laptop.

What you see is the picture of a laptop.

Not meant to be funny. But this simple fact does have many implications and applications. The wikipedia page explains more:

[This] is also cited as an underlying principle used in neuro-linguistic programming, where it is used to signify that individual people in fact do not in general have access to absolute knowledge of reality, but in fact only have access to a set of beliefs they have built up over time, about reality.

Note that neuro-linguistic programming is related to computer programming in the same way as Java is related to JavaScript.