But many investors and others may not know what the market circuit breaker is and why it is so important. What is a market circuit breaker? How does a circuit breaker work? What are single-stock ...

The S&P 500 plummeted 5%, hitting the Limit Up-Limit Down rule, which suspended trading, just minutes after the market opened at 9:30 a.m. this morning. So, what does this mean for the markets? That's ...