Nasdaq is an index that contains 3825 stock. we can trade Nasdaq indirectly through QQQ (which follows Nasdaq's performance), Nasdaq also has an inverse ticker (sqqq) which follows the opposite direction of it. The Spx 500 like it's name contains 500 different stocks, in recent years, tesla was added into it. Both S&p 500 and Nasdaq has technology, communication services, consumer cyclical, health care, consumer defensive, industrials, and utilities while s&p 500 has additional real estate energy and basic materials sector. S&P and Nasdaq have common tickers, such as, Google, FB, Apple, Google, and many more...