A betting exchange is a market where punters (bettors) sell and buy bets between themselves. They set their own prices and if the other party accepts it, the deal is done. The exchange as an organisation acts as service provider for displaying the offers, closing the deals between the anonymous parties and settling the accounts. Usually they get a percentage of the net winnings from the winner. The loser does not pay commission to the exchange.

The prices displayed in the back (on the left)  columns have been entered before as a "lay" bet and the prices shown in the lay columns (on the right) have been entered as a "back" bet. As soon as they are taken, the respective stake gets removed.

As long as a market is not closed, any punter can back or lay as many times they want as long it is within their budget. The commission will be based on the final balance of these bets. It is quite possible because of price fluctuations that a punter has entered into transactions amounting to several thousand dollars with various unknown parties, yet the final balance of his transactions is zero, so he will not win or lose anything and consequently he will not pay any commission.

.