How Polymarket trading works — a plain-English guide

If you've never traded a prediction market, none of it is complicated once you see the shape of it. This is the ground floor: what a price actually means, the two things you can do, and what happens after you've done them.

Every market is a yes/no question

A Polymarket market is just a question with two possible answers — "yes" or "no". Its price is the market's best guess at how likely the answer is "yes". That price runs from 1¢ to 99¢, and you can read it straight off as a percentage: 30¢ means roughly a 30% chance.

Here's the part that makes it a trade. Each share pays out $1 if the answer turns out "yes", and nothing if it doesn't. So if you buy a share at 30¢ and you're right, you get $1 back — about 3.3× your money. Buy it at 80¢ and the market already thinks it's very likely, so being right only returns $1 on 80¢ staked. The cheaper the price, the bigger the payout — and the less likely the market thinks it is.

The two sides of every trade

There are only ever two things you can do, and they're mirror images:

Back · Buy · Yes — you think the answer will be yes. You profit if it happens.
Lay · Sell · No — you think it won't. You profit if it doesn't happen.

Those are three names for the same two actions. Desk shows them in whatever language you read fastest — Back/Lay for sports, Buy/Sell for financial markets, or plain Yes/No — but underneath it's identical. Backing "Yes" and laying "No" are the same bet; you're always choosing which side of the question to stand on.

Good to know

Because the two sides add up to one certainty, a "yes" at 30¢ implies a "no" at 70¢. Buying one is the same as selling the other — there's no separate market to hunt for.

Taking a price vs resting an order

When you place a trade you're doing one of two things:

Taking — you accept the best price on offer right now, so your order fills immediately. You get in straight away, at the price the market's already showing.
Resting — you ask for a better price than the market is currently offering. Your order sits and waits until someone trades against it. It might fill in a second, in an hour, or never — but if it does, it fills at your price.

Taking is certainty of a fill; resting is certainty of a price. Most of trading is choosing which one matters more in the moment.

Your position, your P&L, and trading out

Once a trade fills you hold a position — the shares you own on one side of the question. As the price moves, so does your P&L (profit and loss): the amount you'd walk away with if you closed right now. It's a running total, not a result — it only becomes real when you act on it.

You don't have to wait for the market to resolve to take that number. Trading out — also called greening up or flattening — means closing your position early by trading the other side, locking in whatever profit or loss is on screen. If your "Yes" shares have risen from 30¢ to 50¢, trading out books that gain now, win or lose later. See greening up / trading out for how Desk does it in one click.

That's the whole loop: a price that's really a probability, two sides to take, a fill that's immediate or patient, and a position you hold until you either let it resolve or trade out. Everything else in this guide builds on those few ideas.