How do I make a patch with email?

Apparently it's possible to make patches to code with email, which is stated in GIT-AM(1); but I don't know what the definition of an <Maildir> or <mbox> is.

Update: I think <Maildir> refers to a directory of patch files (typically generated with git format-patch); <mbox> refers to a patch file (generated with git format-patch).