The "Double" is a bet where two (2) selections are made and if the first wins, everything that would have been returned is then used as stake for second.
his style of bet is popular because it creates the potential for larger returns but at the expense of increased risk as all it takes is one losing selection for the bet to return nothing. Similar to the "treble" and "accumulator" the only difference being a lower number of selections. "Each way" and "to-place only" options are also available at some bookmakers.
Popular in all sports especially football and horse racing, all bets in a "double" must be on separate events.