This is the most traditional kind of wager that you can place. When you place such a bet, what you are basically saying is that you think your chosen selection will go on to win the sport event, whatever sporting event that may be. If your selection does go on to win, then you will win your wager and make a profit. It is called a back bet because if, for example, you choose a horse to win the Grand National, you have backed that horse to win.