A win bet is the most simple (and most popular type) of bet, where you bet on a particular horse, team or player to win. The odds offered by the bookmaker reflect the chance that they think your selection has of winning. For example, if a horse is offered odds at 4/1, the bookmakers are predicting that for every 5 times the race is run, the horse would lose 4 times, and win just once, giving it a 20% chance of winning.
If you placed a £10 stake on this horse to win, and it came in first, you would receive 4 times your stake, plus your original stake is returned. This works out to (4 x £10) + £10 = £50.
Another example is a bet on the eventual winner of the Barclays Premiership. Chelsea might be given odds of 8/13 (a 61.9% chance) of coming out on top. If you placed a £10 bet on Chelsea, and they won, your winning would be calculated as follows:
£10 stake returned + (£10 x 8/13) = £10 + £6.15 = £16.15
See our guide to odds for more information.