The main feature, which is also one of the great advantages of trading on bet fair and then more generally of the Betting Exchange, is that you can bet either on the occurrence (back) and on the non-occurrence (Laying) the outcome of sports, in practice you can become like a real bookmaker for a fixed term that is until we believe that the outcome will not occur. You got it! You may decide to close the position even while the event is in progress: imagine, for example, to bet that team will not win. We bet at the beginning game by laying the odds to others and then backing it at half time profiting regardless of whether the outcome is not yet complete (as long as until then the outcome against which we bet has not occurred). The possibility therefore are manifold. So whether we want to trade the odds, or whether we want to play a simple bet, it's smarter to play it in the Betting Exchange because the odds are higher (when we win, we win more) and are not going to pay the gain to the bookmaker. With this observation you can easily understand why the betting exchange came so late in the most part of Europe, because of the interests of a very "strong" lobby of the gambling. Now, however, we can take full advantage of this new and exciting opportunity!