Mii Village is similiar to the Nintendo Village, except you cannot do anything but look at your Mii's. It can also play out a bit like the sims,but with no ageing or dying, with the ability to give your sims jobs & tasks. Otherwise, it is uninteresting.
Mii Plaza is a place where all the Mii's you own appear. You can also create new Mii's & download new ones.
Mii Quest plays a bit like the one from the Nintendo 3DS, except with a twist. Instead of your Mii getting captured, a giant robot comes & sucks all the colour from the world, before slowly deleting all data in the Nintendo Matrix network. Your Mii then sets out on a quest to stop the robot, using Rpg Elements aswell as the ability to turn Mii's found via Streetpass into one of your 3 allies.