> > I want to know more about the closures in Emacs
> 
> Maybe a good starting point is
> wikipedia.org/wiki/Closure_(computer_programming)

Yes.  Here's another (closures in Lisp, not Emacs).

https://www.youtube.com/watch?v=aAlR3cezPJg

This is Scheme in Scheme.  But same idea.

You can show the full transcript (click "..." below
the video on the page), and search it for "closure",
if you like (11:42, 12:45, 19:10, 20:10, 45:52,
46:30, 47:07, 48:33, 48:57, 49:17).  But for more
fun, start at the beginning...