Msd6

I'm a little confused what the MSD 6 does. I do know that it can be wired in conjunction with the mopar electronic ignition. I told a buddy that I was going to get a nitrous set up for my Dart and he said I needed an MSD6 but couldn't tell me what it did or why I needed it. Any info on this would be greatly appreciated.
Good thing your on this forum, what exactly do you have for drivetrain, and how much spraydo you want to use, and why? Too much Nitrous and inexperiance is a bad combo, IMO