Introduction to MacPorts Please?

[Diane White]

Please excuse me, but what exactly is MacPorts?  How does it work?  Is it
really what I want to use?  I found Mac Ports through looking at another
program called Jailkit, and there was another website (the predecessor to
MacPorts?) called DarwinPorts.  Unfortunately, the main page of MacPorts
does not have a simplified "This is what this is, this is what it does" type
of introduction, and I find that to be enormously helpful in putting myself
in the right mindset for what I am dealing with.  

Essentially what I'm trying to do is create an automated updater on a client
computer that logs into the server using sftp and downloads updated files
from a certain directory.  The server is Mac OS X 10.4.9, and I would like
the account that the updater uses to be chrooted to the download directory.
Based on my research so far, chroot is broken with the OpenSSH server unless
you install a patch or do other stuff, which I'm trying to minimize messing
with the current settings of the server and was really hoping to just have a
restricted user or group account.  

The jailkit program seemed like a simple solution, but to use it on the Mac,
I would have to install MacPorts?  Or is this just introducing another mess
for myself?  I'm not even positive at this point if that's what I really
want to use...

Thank you.  
Diane