How Markets Work
22 min
Lesson 3
Foundations › How Markets Work

Market Makers & Liquidity

Someone always has to be willing to buy when you want to sell. Market makers make that possible — for a price. Understanding how they profit helps you understand why spreads exist and when they widen.

Who is a Market Maker?

A market maker is a firm (or person) that stands ready to buy and sell a security at any time, posting both a bid and an offer. Their profit comes from the spread — they buy at the bid and sell at the ask, pocketing the difference.

On the NYSE, specialist firms have legal obligations to maintain fair and orderly markets in the stocks they cover. On NASDAQ, market maker firms compete against each other. Either way, they're the counterparty to a large chunk of retail orders.

The Spread as Payment for Insurance

When you buy at the ask, you're paying the market maker to take the other side of your trade immediately. That convenience costs the spread. In highly liquid large-cap stocks (AAPL, MSFT), the spread might be a penny. In smaller or less-traded stocks, it could be 5, 10, or 20 cents — a real drag on returns.

When Market Makers Step Away

In normal conditions, spreads are tight and execution is fast. But during earnings, economic announcements, or extreme volatility, market makers widen their spreads dramatically — or step back entirely. This is why you see wider spreads and slower execution during high-stress market moments. They're pricing the uncertainty, not abandoning you.

Level 2 / DOM — Reading the Book

The Level 2 display (also called the DOM, or depth-of-market) shows you the full order book — not just the best bid and ask, but the queue of orders behind them. Large buy walls (lots of limit orders at a price) can signal institutional support. Large sell walls signal resistance. Learning to read the book adds a layer of context your price chart alone can't provide.

Penny Pricing & Payment for Order Flow

Some brokers send retail orders to market makers in exchange for payment — this is called payment for order flow (PFOF). The broker gets a fee; the order still gets executed, but you may not be getting the best possible price. This is one reason to care about execution quality and the broker you choose.

Key Takeaways

Module Complete

You've just completed How Markets Work. You now understand the plumbing: how trades execute, how orders flow, and who stands behind every price you see. These foundations will make everything else in this course sharper — because you'll never mistake the visible chart for the full picture.

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