Start wherever you like. You don't need to memorise these words before trying to understand the ideas. On our How it works page, the first unfamiliar term has a little ? you can tap or select with your keyboard for a quick explanation. Here you'll find a slightly fuller answer.
1. Start with the basics
A bookmaker, an exchange and a free bet are different things. Here are the words you'll meet first.
Bookmaker
A business that accepts bets and sets the odds. You choose a result, place your bet and see what happens.
For example: You bet £10 with a bookmaker on a football team to win.
Matched betting
A way of placing bets on opposite results, usually a bookmaker bet and a lay bet on an exchange, to try to make use of eligible promotions without relying entirely on picking a winner. The process has costs and mistakes can lead to losses.
For example: Lay off an eligible qualifying bet, then assess how to use and separately lay off any free bet awarded.
Odds
The numbers showing how much a winning bet would pay. Bigger odds usually mean a less likely result and a bigger payout if it happens.
For example: At decimal odds of 2.00, a winning £10 bet pays £20 including your original stake.
Back bet
A bet that something will happen, such as a team winning or a horse finishing first.
For example: Betting on Aston Villa to win is a back bet.
Betting exchange
A service where customers bet against one another. Unlike a bookmaker, it lets you bet for or against an outcome.
For example: You can bet against the team you've backed with the bookmaker.
Lay bet
A bet against a particular result. Laying off a bookmaker bet means taking the opposite side on an exchange to help balance the possible results.
For example: Back a team to win with a bookmaker; lay that same team on the exchange.
Lay stake
The amount you offer on an exchange when betting against an outcome. It isn't necessarily the amount you could lose.
For example: A matching calculator can suggest a lay stake based on both sets of odds.
Liability
The amount you could lose on an exchange lay bet if the result you're betting against actually happens. You must have enough money to cover it.
For example: Laying £10 at odds of 3.00 has a £20 liability, before any fees.
Qualifying bet
An ordinary bet made with your own money to meet the rules of a promotion. Placing it doesn't automatically guarantee that you'll receive a free bet or refund.
For example: An offer may require a bet of a particular size, at certain odds, by a deadline.
Qualifying loss
The small cost that can remain after correctly backing a selection and laying it off, including any exchange fees. It can be larger if prices move or something goes wrong.
For example: The two bets might leave a small cost before the offer gives you anything.
Free bet
A promotional bet awarded under an offer's rules. It isn't cash: some free bets don't return the stake as part of any winnings, and restrictions can apply.
For example: A £10 free bet does not necessarily let you withdraw £10 or keep £10 after costs.
Oddsmatching
A tool for comparing bookmaker odds with exchange odds, helping you find bets that can be paired and calculate whether the costs look reasonable.
For example: It may highlight an eligible selection with similar prices on both sites.
2. Offers, refunds and costs
Once the first offers are familiar, the challenge is following the conditions and working out what a free bet might actually be worth.
Money-back offer
A promotion that gives something back if a stated condition happens. 'Money back as a free bet' normally means a free bet, not a cash refund.
For example: A losing qualifying bet may earn a free bet if every offer condition is met.
Reload offer
A promotion that some bookmakers offer to existing eligible customers after their introductory offers. Availability is not guaranteed.
For example: A bookmaker might run an occasional refund or extra-place promotion.
Hedge / lay off
Place another bet that helps offset the outcome of your first one. In matched betting this often means laying the same selection on an exchange.
For example: You lay off the original qualifying bet, then may separately lay off any awarded free bet.
Exchange commission
A fee some exchanges take from net winnings in a market. The rate and the way it is charged affect the result.
For example: A calculator should allow for the exchange's current commission before showing an estimated return.
3. Advanced ideas, still in plain English
Some tools look for unusually attractive odds instead of simply pairing opposite bets. That changes the level of risk.
No-lay betting
Placing a bookmaker bet without a matching bet against it on an exchange. If your selection loses, you can lose your entire stake.
For example: An advanced tool flags a possible value bet, but you choose not to lay it off.
Expected value (+EV)
A way of asking whether the odds might be better than the true chance of winning suggests. It's an estimate, not a guarantee that a bet will win or be profitable.
For example: A tool might flag odds it considers generous, even though the selection could still lose.
Variance
The difference between what a strategy might be expected to do over many bets and what actually happens along the way. Losing runs can be long.
For example: Even bets that seem good value may lose repeatedly.
Account restrictions
Limits a bookmaker may place on betting amounts, offers or account access under its rules. Services cannot guarantee that restrictions won't happen.
For example: An account may stop being eligible for promotions or face lower bet limits.
Ready for the bigger picture? See how sign-up offers, refund offers and advanced tools fit together. If you're considering a subscription, the software reality check explains what to ask before paying.
Editorial references reviewed 28 October 2026: Betfair Exchange on lay bets; Betfair on commission; UK Gambling Commission on offers and conditions; ASA guidance on matched-betting advertising; ASA guidance on free-bet wording. These are definitions for education, not live offers or profitability claims.