I'll start with the VERY basics
Torsion bars are like leaf springs or coils in other applications. Larger bars need more "force" to make them give, so you get a firmer ride etc.
Hollow bars are lighter and some say work better for a number of reasons, but others disagree. They ARE lighter though.
Torsion bars handle the bulk of the work, similar to the leaf springs/coils mentioned above. Anti roll bars (sway bars) act as helpers to the primary spring/torsion bar/coil etc.
There's my $0.00002 worth
EDIT : Never mind, I type too slow!!!
-Chris