Founded in 1971 by the National Association of Securities Dealers (NASD), the Nasdaq Stock Market is the second-largest exchange in the world by market capitalization, after the New York Stock Exchange. It officially separated from the NASD and began to operate as a national securities exchange in 2006.

NASDAQ, the “National Association of Securities Dealers Automated Quotations”, was at first just a quotation system and didn’t actually trade stocks. As the Nasdaq Stock Market got going, it included a lot of stocks that traded as speculative over-the-counter (OTC) issues.

But as the Exchange became the first U.S. stock market to start trading online, it attracted new tech companies who saw it as a more modern, more dynamic place to list their stocks. Those companies included, Apple, Cisco, Dell, Microsoft and Oracle and a host of others.

The exchange’s heavy weighting toward tech and other “riskier” issues lets investors use it as a barometer of how much risk investors are willing to take on at any one time.

The Nasdaq Stock Market has a pre-market session from 4:00 am to 9:30 am Eastern, a normal trading session from 9:30 am to 4:00 pm, and a post-market session from 4:00 pm to 8:00 pm.

It has three market tiers: Capital Market (small-cap) is an equity market for companies that have relatively small levels of market capitalization; Global Market (mid-cap) is made up of stocks that represent the Nasdaq Global Market, consisting of 1,450 stocks that meet Nasdaq’s strict financial and liquidity requirements; and Global Select Market (NASDAQ-GS large cap), consisting of 1,200 stocks and more exclusive than the Global Market.