Stock Market

What the stock market is, in one sentence

A stock market is a public venue for buying and selling small ownership stakes — shares — in companies that have chosen to list themselves for public trading. When you buy a share of Apple, Microsoft, or any other listed company, you are buying a transferable claim on a slice of that company's future earnings and, in most cases, a fractional vote in its corporate decisions.

The price that appears on a quote is simply the last price at which a buyer and a seller agreed to exchange one share. That number moves continuously during market hours because expectations about future earnings, interest rates, and the broader economy are constantly being repriced by thousands of participants.

The headline US indices

US equity coverage usually centres on four widely quoted indices. Each one measures a different slice of the market:

• S&P 500. A capitalization-weighted basket of roughly 500 of the largest US companies, spread across every major sector. This is the index most often quoted as "the market."
• Nasdaq Composite & Nasdaq-100. Tilted heavily toward technology and growth companies. The Nasdaq-100 is a narrower, more tradable version used as a benchmark for tech-heavy funds.
• Dow Jones Industrial Average. A price-weighted average of 30 large US companies. Less comprehensive than the S&P but historically the index most quoted in mainstream news.
• Russell 2000. Tracks 2,000 smaller US companies and is the standard reference for US small-cap performance.

None of these indices is "the" market in a strict sense. Short-term moves often diverge — small caps can rally while mega-cap tech sells off, or vice versa — and watching more than one index is how practitioners spot those rotations.

How a share price actually moves

A stock's price at any moment is set by the balance of limit orders sitting on the order book plus the market orders that hit it. Simplified, when more money wants to buy than sell at the current price, the price walks up until those buyers are satisfied or give up. When more money wants to sell, the price walks down. "News" — earnings, macro data, a central bank decision — changes what participants believe a share should be worth, which shows up almost immediately in those orders.

Two broad drivers sit behind most price action:

• Fundamentals. Revenue growth, profit margins, guidance, cash flow, balance-sheet health, and longer-run prospects. Earnings season, held roughly four times a year, is when fundamentals get their biggest repricings.
• Macro conditions. Interest rates, inflation, the business cycle, currency moves, and fiscal policy. Rate changes are especially important because they set the benchmark return that equities compete against.

Trading sessions and when the numbers move

The core US cash session runs from 9:30 a.m. to 4:00 p.m. Eastern Time, Monday through Friday. A pre-market session starts around 4:00 a.m. and an after-hours session extends until roughly 8:00 p.m., though liquidity is much thinner outside the cash session and spreads widen accordingly. Most of the day's volume is concentrated in the first and last 30 minutes.

Global equity trading is a relay. European markets open before the US cash session and the Asian session precedes Europe, so what happens overnight in Tokyo or Frankfurt often sets the tone for the US open. The home page shows the current New York time and whether the cash session is open.

Sectors and why they matter

The S&P 500 is split into eleven sectors — Information Technology, Financials, Health Care, Consumer Discretionary, Communication Services, Industrials, Consumer Staples, Energy, Real Estate, Utilities, and Materials. Sectors respond differently to macro conditions. Rising rates tend to pressure Real Estate and Utilities while benefitting Financials; falling oil prices lift Consumer Discretionary but hit Energy. The sector heatmap above shows, at a glance, which parts of the market are leading and lagging today.

Reading a quote

A stock quote usually packs several pieces of information into one line:

• Last / price. The most recent traded price.
• Change and change %. Move since the previous close, in absolute and percentage terms.
• Volume. Number of shares traded so far. Unusual volume often signals that something material is happening.
• Day range & 52-week range. Where the current price sits relative to recent highs and lows.
• Market cap & P/E. Company size and a rough valuation metric — useful but never sufficient on their own.

How to use this page

The widgets above let you move from the big picture to the detail without leaving the page. Start with the market-overview widget to see how headline indices closed, drop into the screener to pull up a watchlist filtered by market cap or sector, use the heatmap to find where the day's action is concentrated, and check the earnings calendar before the next session so you know which reports are coming. For deeper charting with technical indicators and drawing tools, see the Advanced Charts page.

Last reviewed on April 24, 2026. Information on this page is general in nature and is not a recommendation to buy or sell any security. See our Disclaimer.