You can use that field do access any directory inside your homedir. So if
you used let's say pine on the Raq, you could read the directories "mail"
and "sent-mail" just as if you were inside pine. That is the huge
advantage of IMAP: you can create a mail tree that will follow you
everywere (as long as you have an IMAP client).
Better than that, smart clients like Netscape, know the folders you
"subscribed" (the ones you store your mail in) and automatically get them
without you having to supply any further info.