I'm using SCB Online trading to buy into AAPL, but the stock exchange stated is NMS? What is NMS and where am I buying the stock from?

NMS stands for the National Market System, which governs the major exchanges in the US such as NASDAQ and NYSE. Since AAPL is listed on the NASDAQ, that is where your will be buying your stock from.

From SCB online trading page: NASDAQ (NMS)

Apple is listed on NASDAQ.

https://investor.apple.com/investor-relations/s...