[ale] What's the alternate function mode on the keyboard for?

[Jim Lynch]

Some if not most of my keyboards have a "F" or mode key that changes the 
normal function keys f1-12 into something else.  If I run xev to see 
what the keys send in the "not" function mode, some of them don't work 
at all.  How can a key not produce any events?

Anyway I discovered this alternate mode the hard way, it got turned on 
by accident an I though I had trashed my keyboard somehow so I bought a 
new one.  Eventually the new one did the same thing and I got to looking 
at the funny lights and discovered this "feature" (?).

So what's it for?  What good is it if it doesn't send any events?

Thanks,
Jim.