Windows drive mapping conventions

I'm installing a nice Linux database server for some folks on hardware
that is currently running an NT 4 file/print server. Naturally they
want to keep their file and print services so I need Samba on the Linux
machine. I've been messing with Samba at home and I think I've mastered
it. It really seems to be very easy to set up.

There is one thing that I simply can't remember from my brief sentence
in the windows world and that is the convention for 'p' and 'm' drives.
I remember that one is supposed to be mapped to the users home
directory and the other is supposed to be mapped to a shared directory
but I can't for the life of me remember which is which. I did Google
for it but I found one reference that said 'p' is for public drive and
'm' is the other one while a different reference said 'p' is for
private drive and m is the other one. I couldn't find anything from a
source that could be considered authoritative. I guess this is just
something that Windows users know.

What is the real convention, if there is one? Can anyone satisfy my
curiosity as to why it's 'p' and 'm'?