The close refers to the time when trading
ends for the day. The close is typically is set by the exchange where
the security is traded, and varies depending on the exchange and the
security being traded.
The second meaning of close is the price of the security at the end of trading time of the day. This is also commonly referred as close price. This is opposite of open price.
For example, in the United States, the New York Stock Exchange (NYSE) and NASDAQ both close at 4:00 PM Eastern Time, while the Chicago Mercantile Exchange (CME) and Chicago Board of Trade (CBOT) close at different times depending on the security being traded.
After the close of regular trading hours, some exchanges offer after-hours trading, which allows traders to buy and sell securities outside of regular trading hours. After-hours trading typically lasts from 4:00 PM to 8:00 PM Eastern Time in the United States.
It's important to note that after-hours trading carries additional risks and may not be suitable for all investors. After-hours trading can be more volatile and have wider bid-ask spreads than during regular trading hours, which can lead to higher trading costs and greater risk of losses.
In summary, the close refers to the time when trading ends for the day on a particular exchange. The close time varies depending on the exchange and the security being traded. After-hours trading may be available for some securities, but carries additional risks and may not be suitable for all investors.