Hi
Yes, you can quantize single note or selection of notes. You can say that you want all Cs to be quantized, or you can quantize only one measure.
Knowing that the sequencer is 96ppqn is often very useful. I have a couple of examples: First, when you quantize something, you kvow that it will be placed on clock-ticks 24, 48, 72 etc as dnarkosis said. When you use the Microscope-mode, you get to see all MIDI-events in the sequencer, and they are placed by measure, beat and clock tick. One other situation where it comes handy to know about this, is when setting up effects. Many of the effects use this clock-tick as a reference, so you can have a delay that is exactly 1/2 measure etc.
It is helpful to know that the sequencer works in this way, because you will meet the clock-reference when using sequencer, effects, programming patches etc.
Hope this got a bit clearer now?

Stig