Why would I want to format a 1.4 meg diskette in ProDOS? ?

[Rocket Press...a Litmag <rocketusa@delphi.com>]

Okay, here's my latest query, with bonus editorial!
 
This selection has to do with formatting - and I never want to sound dumb, I
just have no formal technical training and figure it's better to ask than to
just sit bavk and let the computer run ME.
 
This selection also has to do with Mac's System 7.5.
 
This selection has to do with a young man who meets a young girl.
 
[Hey, if we don't keep these Apple II groups active, the Net gods will cancel
us like they've done with Atari and others.]
 
Anyway, I was on whatever system Appleworks GS goes on. I went to format and it
gave me these options:
prodos 800k 4:1
prodos 800k 2:1
prodos 400k 2:1
Now, why would I want a 400k disk? Is this the same as a single side
initialization?
I know olden Macs could use the 400k, but Apples IIs?
 
Scene II:
I work at a newspaper where there Macs, one of which uses 7.5. It's not my
computer with the 7.5, but I go over to it whenever I do my work at home or
want to bring work home, since there isn't Apple File Exchange anywhere.
 
The machine use to give the option to format in 800k Mac or ProDos or 720k DOS.
This was fine since I could bring in my 800k gs disks or 720k DOS disks if,
for some strange reason I wanted to use my PC Transporter.
 
But today I went in with my prodos 800k disk and stuck it into the 7.5 mac
and the thing said this disk is unreadable. Would I like to reformat it?
Then it gave me these options:
Prodos 1.4 meg
Dos 1.4 meg
Mac 1.4 meg
 
Did the operator of this computer change it's settings for formatting?
What would I do with a 1.4 meg ProDos disk? Is there a GS system that can
handle 1.4 meg?
Would changing the settings back to 800k, 720k, on the Mac simply involve going
under the apple and finding settings and switching them back, then restarting
(I hate playing with other people's computers)?
I tried sticking an 800k Mac disk in there and the 7.5 couldn't read that
eitherand was urging me to reformat that sucker.
 
I love you guys for all the help and knowledge you always throw my way...
 
Darren