TRADING / PRACTICAL GUIDE

Stock Market Basics: A Clear Starting Point

A stock is a small ownership slice of a company, bought and sold through a broker on an exchange or similar venue. The number on your screen is the latest price two willing traders agreed on — it shows where opinion sits right now, not where the company is guaranteed to go next.

By Mika vs Guru Editorial Team · Reviewed 18 September 2026 · About 5 min read

What actually happens when you click buy

You place an order: You tell your broker what to buy, how many shares, and under what conditions — for example, "buy 20 shares of XYZ at the market price."
The broker routes it: Your broker sends the order to an exchange, another broker, or an internal matching system, depending on where it can be filled under the order's terms.
It matches against a seller: A buy order fills once it meets a seller willing to trade at a compatible price. That can take a fraction of a second in a liquid stock, or longer in a thin one.
It settles: The trade shows up in your account right away, but ownership officially settles a short time later, when cash and shares actually change hands.

Price is an agreement, not a verdict

Picture a company called Northfield Robotics trading at $42.00. A supplier announcement lands, and within an hour the price is $44.10. Nothing about the machines Northfield builds changed in that hour — what changed is what buyers and sellers were willing to accept, given the new information and how each side read it.

That is the entire mechanism behind every quote you will ever see: a running, public agreement between whoever is willing to buy and whoever is willing to sell at that instant. A well-known company can still be a poor trade at $44.10, and an obscure one can be a good trade at $2.00 — the price alone doesn't settle the question.

Five building blocks worth learning before you trade

Ticker symbol: The short code that identifies a specific stock on an exchange, usually three or four letters.
Bid and ask: The bid is the highest price a buyer currently offers; the ask is the lowest price a seller currently accepts. The gap between them is the spread.
Order types: A market order trades immediately at the best available price. A limit order only trades at your chosen price or better, and may not fill at all.
Trading sessions: Regular-hours trading has the most participants and the tightest spreads. Pre-market and after-hours sessions exist but usually have thinner liquidity and wider spreads.
Position size: How many shares you hold decides how much a given price move affects your account — not just whether you were right about the direction.

Northfield, one week later

Take the same company a week on. Northfield Robotics is quoted at $43.80 bid and $43.86 ask during regular hours, and about 400,000 shares have traded by lunchtime. You want 20 shares. A market order fills almost instantly at $43.86 — you pay the ask, and the six-cent spread is the cost of immediacy. Twenty shares at six cents is $1.20, which barely matters here.

Now try the same order at 6:30 in the evening, after the regular session. The quote is $43.40 bid and $44.30 ask, and only a few hundred shares have changed hands. The same market order could fill at $44.30, well above where it last traded during regular hours, because that is simply the best price anyone is offering at that hour. Nothing happened to the company. The room got emptier.

A limit order at $43.90 would sit and wait. It might fill, it might not, and if the stock opens higher tomorrow you have no position at all. That is the trade-off every order type carries: the market order guarantees a fill but not the price, and the limit order guarantees the price but not the fill.

Where the simple picture gets complicated

Halts: An exchange can pause trading in a stock around major news or unusual volatility. While halted, no order fills at any price, and the first trade afterward can be far from the last one before it.
Fractional shares: Some brokers let you buy a slice of one share. Convenient, but the fractional part is usually held and routed by the broker in its own way, so check how it can be sold.
Where the order goes: Two brokers can send an identical order to different venues and get slightly different prices. The difference is often a cent or less, but it is real, and it is one reason broker order guides are worth reading.
Settlement dates vary: How long official settlement takes depends on the market and the type of security. Until it settles, some brokers restrict what you can do with the proceeds.

Common mistakes at the start

Treating the price as the value: A $5 stock is not cheap and a $500 stock is not expensive. Price per share says nothing until you know how many shares exist.
Using market orders in thin stocks: In a stock that trades a few thousand shares a day, a market order can fill several percent away from the last print.
Confusing the quote with a fill: The last price is history. Your fill comes from whoever is on the other side when your order arrives.
Sizing by feel: Buying "a hundred shares" because it is a round number ignores what a normal daily move in that stock does to your account.

What this guide does not cover

This is a starting point, not a complete map. It leaves out options, margin borrowing, short selling, dividends and how they are taxed, and how order routing differs between brokers. Each of those changes the risk picture in ways worth learning on their own — treat this guide as the floor, not the ceiling.

What to do next

Open your broker's order ticket without submitting anything. Find where the order type, the time-in-force and the session setting live, so you are not learning the layout with money on the line.
Read the bid, ask and spread on three stocks of different sizes at the same moment. The difference between a large company and a small one will tell you more than any definition.
Watch one stock for five sessions, as in the exercise below, before placing a first trade. Then start with a quantity small enough that a bad fill is a lesson, not a loss you notice.

Sources and further reading

Continue learning

Educational purpose: This guide provides general education. It does not provide personalised financial, investment, legal or tax advice.