What are extended hours trading?

Question

I've seen this before the U.S. market opens, but how does it work and is it any indication how the regular market will do?

Answer 1

Some stocks are listed on multiple exchanges. Exchanges do not all share the same hours. I knew some people who used to trade in the regional exchanges, so when New York or Boston or Philadelphia had closed with a trend, they would continue it on the Pacific. Today there are also various electronic exchanges as well.

Answer 2

http://www.best-stock-trading-systems.com/After_Hours_Stock_Trading.html