Okay kiddo, so let me explain what Regulation NMS is. You know how in some games there are rules you have to follow so that everyone can play the game fairly? Well, Regulation NMS is like those rules but for the stock market.
Basically, the stock market is where people buy and sell pieces of companies, called stocks. But it's really important that everyone plays by the same rules so that no one person can cheat or have an advantage over others. That's where Regulation NMS comes in.
One of the most important things it does is it requires that trade orders happen at the best available price. That means if you want to buy a stock, you have to buy it at the lowest price someone is selling it for. And if you want to sell a stock, you have to sell it at the highest price someone is willing to buy it for.
Regulation NMS also makes sure that everyone has access to the same information about the stock market at the same time. That way, no one person or company can get information that others don't have and use it to make unfair trades.
Overall, Regulation NMS helps to make sure that the stock market is fair and works the way it's supposed to.