From the apt-get man page:
Fix; attempt to correct a system with broken dependencies in place.
This option, when used with install/remove, can omit any packages
to permit APT to deduce a likely solution. If packages are
specified, these have to completely correct the problem. The option
is sometimes necessary when running APT for the first time; APT
itself does not allow broken package dependencies to exist on a
system. It is possible that a system's dependency structure can be
so corrupt as to require manual intervention (which usually means
using dselect(1) or dpkg --remove to eliminate some of the
offending packages). Use of this option together with -m may
produce an error in some situations. Configuration Item:
Search string: "man apt-get"