Every day at the New York Stock Exchange, $80 billion changes hands. Who are the people making the big deals? Traders, of course. Maria says 2,500 traders buy and sell stock during market hours, which lasts from 9:30 a.m. to 4 p.m. ET.
Thousands of companies also trade off Wall Street, and all together, they're valued at nearly $24 trillion, Maria says.
On the floor of the stock exchange, there are areas called trading posts, where actual companies are traded.
"If you want to buy something on eBay, you've got to find somebody to sell you that product," Maria says. "It's the same thing that happens in a stock market, only here at the New York Stock Exchange, there's a human being who brings together you the buyer, with someone who is going to sell you that stock."