After-hours market

Securities, such as stocks and bonds, may change hands on organized markets and exchanges after regular business hours, in what is known as the after-hours market.

These electronic transactions explain why a security may open for trading at a different price from the one it closed at the day before.

There's also trading in benchmark indexes such as Standard & Poor's 500-stock Index (S&P 500) and the Dow Jones Industrial Average (DJIA) before US stock markets open. The level of activity and the direction the trading — up or down — is widely interpreted as an early indicator of what's likely to happen in the market during the day.