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Now that you can read a book, you need to tell the exchange what to do with it. This chapter covers the two orders you’ll use for almost everything — market and limit — and the maker/taker distinction that decides what you pay in fees.

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Two Ways to Trade

When you want to buy or sell shares, you have two basic choices:
  1. Market order — “I want to trade right now, at whatever price is available”
  2. Limit order — “I want to trade at this specific price or better”

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Market Orders

A market order says: “Just get it done.” You don’t pick a resting price — the exchange matches you with the best available offers on the order book immediately.
On Kairos: a market order still requires a price. Kairos treats it as the limit you authorise it to cross to, not as a “any price” sentinel, and rejects the order without one. Send the live same-outcome quote — ask for buys, bid for sells. See Order Types for the API details.
When to use it:
  • You want to trade right now
  • You care more about speed than getting the perfect price
  • The order book has enough depth at reasonable prices
The catch: If there isn’t much depth, you might get a worse price than expected. This is called slippage (covered in a later chapter). Example: You market buy 100 shares. The book has 80 at 0.55and150at0.55 and 150 at 0.57:

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Limit Orders

A limit order says: “I’ll only trade at this price or better.” You set your price. If the market can fill you at that price (or a better one), it does. If not, your order waits. When to use it:
  • You have a specific price in mind
  • You’re not in a rush
  • You want to control your cost
You: Limit buy 100 at $0.53 Book: Best ask is 0.55∗∗—noonesellingat∗∗0.55** — no one selling at **0.53 Result: Order rests on the book and waits. …later, someone sells at $0.53… Result: Filled!

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Resting Orders

When a limit order can’t fill immediately, it rests on the order book. It becomes a bid (if buying) or an ask (if selling) that other traders can trade against. Your resting order stays on the book until:
  • Someone takes the other side (you get filled)
  • You cancel it
  • It expires (depending on time-in-force settings)
Think of it like leaving a note at the auction: “If anyone wants to sell at $0.53, I’m buying.”

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Maker vs Taker

These terms describe your role in a trade: Why it matters: Many exchanges charge lower fees for makers (sometimes zero). Makers help the market by providing liquidity. Takers pay a bit more for the convenience of instant execution.
On Kairos: the exact maker and taker rates depend on the venue and on your fee tier, and one venue inverts the usual direction. See Fees before assuming maker is the cheap side.

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Quick Comparison

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A Simple Rule of Thumb

  • In a hurry? Market order.
  • Have a target price? Limit order.
  • Want lower fees? Limit order (maker).
Next: Time-in-Force — how long an order should stay alive, and what to do if it can’t fill completely.