I'd suggest doing some searches here and possibly at
T-Mag, possibly looking for stuff from Ian King on the first one.
VERY briefly, periodization has to do with varying your workouts over time and volume has to do with the amount of weight you move, including both number of sets and number of reps. That's the snapshot answer but there's a lot more out there.
EDIT: Rock beat me to it with a MUCH better answer!
