Holy cow, I wrote a book!
The keyboard shortcut for "Minimize All" is
The keyboard shortcut for "Show Desktop" is
How are they different?
"Minimize All" is easier to describe.
It minimizes all the windows that support the "Minimize" command.
You can minimize a window by selecting "Minimize" from its System menu,
or by clicking the
button in the title bar.
So "Minimize All" is effectively the same as going to each window
that is open and clicking the Minimize button.
If there is a window that doesn't have a Minimize button, then it is
"Show Desktop" takes "Minimize All" one step further.
After minimizing all the windows that can be minimized,
it then takes the desktop and "raises" it to the top of the
window stack so that no other windows cover it.
(Well, okay, topmost windows continue to cover it.)
So "Show Desktop" manages to get a few more windows out of your way
than "Minimize All".
Note, however, that when you return the desktop to its normal
state (either by selecting "Show Open Windows" or just by switching
to another window), all the un-minimizeable windows come back
because the desktop has "lowered" itself back to the bottom of the