How the US Stock Market Works: NYSE, Nasdaq and Your Brokerage Account

The US stock market is not one place. It is a network of exchanges, off-exchange trading venues, brokers, market makers and a central clearinghouse, held together by federal rules that require them to route your order to a fair price. Understanding that network explains a lot: why trades are commission-free at many brokers, why a quote can move between the moment you tap buy and the fill, and why your shares are safe even if your broker fails.

The exchanges

A stock exchange is a regulated marketplace that matches buyers and sellers and sets listing standards for the companies it hosts. Two names dominate:

• New York Stock Exchange (NYSE). Founded in 1792 and based on Wall Street in Lower Manhattan, the NYSE combines electronic trading with a physical floor where designated market makers oversee the opening and closing auctions of their assigned stocks. Many of the oldest US industrial, financial and consumer companies list there.
• Nasdaq. Launched in 1971 as the world's first electronic stock market, Nasdaq has never had a traditional trading floor. It became the natural home for technology companies, though today it lists businesses in every sector.

A company has one primary listing, but its shares trade on many venues at once. The NYSE and Nasdaq groups each run several exchanges, and there are other registered exchanges too, such as those operated by Cboe and the Investors Exchange (IEX). All of them compete for order flow.

Off-exchange trading

A large share of retail orders never touch an exchange. Brokers often send them to wholesale market makers, firms that buy and sell from their own inventory and fill retail orders internally. Institutions also trade in alternative trading systems, sometimes called dark pools, where large orders are matched without showing them publicly in advance.

This is legal and regulated. Under the SEC's Regulation NMS, trades generally may not execute at a price worse than the best publicly displayed bid or offer across the exchanges, known as the national best bid and offer (NBBO). Brokers also owe customers a duty of best execution, which means seeking the most favorable terms reasonably available. Some brokers receive payment for order flow from wholesalers, which helps fund zero-commission trading; brokers must disclose these arrangements in their quarterly order-routing reports.

Who regulates what

Before opening an account, it takes two minutes to search a firm on FINRA's BrokerCheck and confirm its registration and any disciplinary history.

What happens when you place an order

Consider a buy order for 10 shares placed in an app during market hours.

1. The broker receives the order and checks you have the cash or margin to pay.
2. The broker routes it to an exchange, a wholesaler or another venue, according to its routing policy and its best-execution obligation.
3. The order is executed against a seller, usually within a fraction of a second for a liquid stock.
4. The trade is reported to the consolidated tape, so the price and volume become public.
5. The trade is cleared and settled. Since May 2024, most US stock trades settle one business day after the trade date (T+1). On settlement day, cash moves to the seller and the shares move to your broker's account at the depository, credited to you.

Your shares are usually held in street name, meaning the broker is the record holder on your behalf, while its books show you as the beneficial owner. You still receive dividends, proxy materials and voting rights.

Order types worth knowing

• Market order: buy or sell immediately at the best available price. Fast, but the price is not guaranteed, which matters in thinly traded stocks or at the open.
• Limit order: buy or sell only at a set price or better. You control price but may not get filled.
• Stop order: becomes a market order once the stock trades at a trigger price, often used to limit losses. In a fast fall, the fill can be well below the trigger.
• Stop-limit order: becomes a limit order at the trigger, which caps the price but may not fill at all.

Orders can also be marked day (expires at the close) or good-til-canceled, which most brokers cap at a set number of days.

Trading hours and auctions

The regular session runs from 9:30 a.m. to 4:00 p.m. Eastern time, Monday through Friday, excluding exchange holidays. Each listing exchange runs an opening auction and a closing auction that pool orders to set a single price; the closing price is the one used for most fund valuations and index calculations.

Many brokers offer extended-hours trading before the open and after the close. Liquidity is thinner, spreads are wider and prices can react sharply to earnings released outside regular hours, so many brokers accept only limit orders in those sessions.

Safety mechanisms

US markets have several automatic brakes:

• Market-wide circuit breakers pause trading across all exchanges if the S&P 500 falls by set percentages from the prior close (7%, 13% and 20%), with the largest triggering a halt for the rest of the day.
• Limit up–limit down bands pause trading in an individual stock if its price moves outside a band in a short period.
• Regulatory halts let an exchange stop trading in a stock pending major news.

Indexes: the market's scoreboards

When the news says "the market" rose, it usually means an index:

• S&P 500: roughly 500 large US companies weighted by market value; the most common benchmark for US stocks.
• Dow Jones Industrial Average: 30 large companies, weighted by share price rather than size, which makes it a narrower gauge.
• Nasdaq Composite: nearly every stock with a primary listing on Nasdaq, heavily weighted toward technology.

Indexes are not things you can buy directly, but index funds and ETFs that track them are covered elsewhere on FC Markets.

What protects your account

Brokers must keep customer securities and cash separate from their own under SEC customer-protection rules. If a broker fails anyway and assets are missing, SIPC protects up to $500,000 per customer, including up to $250,000 in cash, as described on sipc.org. SIPC does not cover market losses, bad advice or investments in unregistered products, and some firms buy additional private insurance on top.

Cash swept into partner bank accounts may be covered by FDIC insurance instead, subject to that program's limits and rules, so it is worth reading how your broker handles uninvested cash.

Putting it together

A quick way to check your understanding: open your broker's order ticket, look at the bid, the ask and the size on each side, and note the difference between the two. That spread is a cost of trading even when the commission is zero. Then read your broker's order-routing disclosure, which shows where orders go and what payments it receives. Ten minutes with those two documents tells you more about how the market really works than most headlines.

This article explains how US stock markets operate and is not investment advice. Rules, hours and protection limits can change; confirm current details with the SEC, FINRA, SIPC and your broker.