The Chinese Room Argument, explained briefly

[Oberon]

You are locked in a room full of boxes containing chinese symbols, and rule book in English for manipulating the symbols. You get as input from the outside some Chinese symbols; you look up in the rule book what you're supposed to do with those symbols, and give back some symbols in Chinese.

Unbeknownst to you, the symbols you get are questions, and the symbols you give back are correct answers, in Chinese, to the questions, such that they are indistinguishable from those a Chinese speaker would give.

Assuming you don't understand a word of Chinese, you still pass the Turing test for understanding Chinese; you fool the other person outside into thinking they really are speaking with someone who speaks Chinese. All the same, you don't understand a single word of Chinese.

If you cannot get from the syntax of the computer program to the semantics of understanding Chinese, then neither can any other digital computer, because no computer has something that you don't have.

TL;DR:

Syntax is not semantics. Computer programs are defined entirely syntactically; operations over syntactical elements.
Human intelligence requires more than just a syntax; it requires a semantics.
Therefore, programs which are syntactical, do not have intelligence.