debmirror: what does 'passive' option mean?

[Tshepang Lekhonkhobe]

Hello,
Debmirror, such a useful tool for me, has the 'passive' option whose
meaning I don't know and would like someone to explain. Also, doesn't
the program sometimes include package files which it doesn't download?
I had a problem where I had the partial mirror and then on install
there were several missing files (a clear case where those were in the
Packages list, but not in pool). It couldn't be my media because I did
a binary compatibility check.
Thanks...