bug#51930: 27.2; Buffer-local functions? Buffers specified buffer-locally?

[Drew Adams <drew.adams@oracle.com>]

I'm trying to read (elisp) `Window Hooks', and I can't make heads or
tails of it.  Throughout this node there's mention of buffer-local
functions: "functions specified buffer-locally".

I have no idea what is meant by this.  I search the Elisp manual for
buffer-local, and I find zillions of matches that are about
buffer-local variables, of course.  And I find a couple of mentions
of buffer-local faces.  No mention, that I can find, of buffer-local
functions or "functions specified buffer-locally".  How to specify a
function buffer-locally?

A wild guess is that what you're trying to say has something to do
with using the LOCAL argument to `add-hook' or `remove-hook`.  But
if so, it's not clear what.

Please clean up this text so it's comprehensible by an average reader.
If buffer-local functions are indeed a thing now, please document what
they are, somewhere.

In GNU Emacs 27.2 (build 1, x86_64-w64-mingw32)
 of 2021-03-26 built on CIRROCUMULUS
Repository revision: deef5efafb70f4b171265b896505b92b6eef24e6
Repository branch: HEAD
Windowing system distributor 'Microsoft Corp.', version 10.0.19042
System Description: Microsoft Windows 10 Pro (v10.0.2009.19042.1288)