Why all the Alt bindings by default?

[Drew Adams]

emacs -Q in Emacs 24, visit an Emacs-Lisp buffer, `C-h b'.
Do the same in Emacs 23.3.

In Emacs 24 (but not in 23.3) I see lots of Alt bindings that presumably (?)
insert characters:

A-SPC            
A-!             ¡
A-"             Prefix Command
A-$             ¤
A-'             Prefix Command
A-*             Prefix Command
A-+             ±
A-,             Prefix Command
A--             ­
A-.             ·
A-/             Prefix Command
A-1             Prefix Command
A-3             Prefix Command
A-<             «
A-=             ¯
A->             »
A-?             ¿
A-C             ©
A-L             £
A-P             ¶
A-R             ®
A-S             §
A-Y             ¥
...

Actually, I don't know what these keys do.  The fancy characters are shown in
the `binding' column.  What does it mean for a key to be bound to a character
(as opposed to command `self-insert-command')?

I don't even know how to hit such keys to see what `C-h k' says.  By default,
Alt is Meta, at least on most platforms.  I tried `(describe-key (kbd "A-/"))'
etc., but that just says "A-/ is undefined".

What's this all about?  

Searching for `Alt', or `A-', or even `Unicode' turns up nothing in NEWS.

Also, (emacs) Modifier Keys says this explicitly:

"Emacs supports three other modifier keys.  These are called
 <Super>, <Hyper> and <Alt>.  Few terminals provide ways to use these
 modifiers; the key labeled <Alt> on most keyboards usually issues the
 <Meta> modifier, not <Alt>.  The standard key bindings in Emacs do not
 include any characters with these modifiers.  However, you can
 customize Emacs to assign meanings to them.  The modifier bits are
 labelled as `s-', `H-' and `A-' respectively."

Apparently it is no longer true that "The standard key bindings...do not include
any characters with these modifiers." (?)