When the market opens at 9:30 a.m., the opening price is the first price a stock trades at, and the closing price is the last price it trades at when the market closes at 4:00 p.m.
It's important to note that trading occurs both before and after markets open, but the majority of transactions occur during regular market hours, so investors and analysts pay close attention to open and close prices to determine whether certain stocks increased or decreased in value during the previous trading session.

The opening price of a stock is the price at which it first trades when the market opens for the day. It is determined by pre-market supply and demand, including overnight news and after-hours trading activity.

The closing price is the final trading price of a stock when the market closes for the day. It is a key reference point for investors, used in technical analysis, performance tracking, and after-hours trading valuations.

The difference between opening and closing prices reflects market sentiment, news, and trading activity throughout the day. Significant gaps between them may indicate volatility or major events affecting the stock. Both prices are crucial for analyzing trends and making informed investment decisions.