The key methods of betting on any specific event, backing and laying refer to the two core things you can do when making a wager – ‘backing’ where you bet on one thing to happen, and ‘laying’, where you bet on it to not. Typically laying is only available on betting exchanges (as bookmakers are effectively laying every price for you), so lets look at the sort of example you encounter on an exchange.
Backing with decimal odds
Say we look at a Premier League football match and see three sets of decimal odds:
Back: 1.81/Lay: 1.82
Back: 3.85/Lay: 3.89
Back: 5.1/Lay 5.2
In this case we could back Manchester united at 1.81, in which case we would be risking 1 unit to win 0.81 units and our stake back.
However, say we are very confident that Chelsea will not win, in this case we could lay Chelsea at 5.2, which will mean that we win on either the draw, or on Manchester United winning. However, as we are now booking the backed price, we are liable to pay out at odds of 5.2 if Chelsea win, meaning we have a liability on the bet of 4.2 units for every 1 we are winning.