What's NC / NW in M.A.C?
--NC means Neutral Cool (people with cooler under tones: i.e, yellow undertones)
--NW means Neutral Warm (people with warmer under tones: i.e, pink under tones)
How would I know my under tone?
--Don't just base it on your face, because most of the time our faces are a lot darker or lighter than our neck & chest area. So make sure you base it on the color of your neck & chest. It'll be a lot easier to find what under tone you are.
Hope this was helpful!
So next time you're at a M.A.C counter /store and you don't know what shade you are or what's your under-tone color, well now it'll be a lot easier for you to remember :)