What is the meaning of "Custom Iteration Hook"?

Question

here is a excerpt from where I got it.

The for...of statement creates a loop iterating over iterable objects, including: built-in String, Array, array-like objects (e.g., arguments or NodeList), TypedArray, Map, Set, and user-defined iterables. It invokes a custom iteration hook with statements to be executed for the value of each distinct property of the object.

Answer 1

I don't know precisely if I'm correct, but I believe "custom iteration hook" refers to the statements inside the for..of block