A combo bet.
Also known as combo bet, ACCA, multiple bet or Parlay (US), is a cumulative bet which includes series of single bets selected by the punter. The more selections are made, the higher are the odds and potential winnings, but also the risk. Most of the times, in order to win the accumulator, the outcomes of all selected events must be predicted correctly and if one of the bets is lost, then the whole accumulator is lost as well. Usually, the punter is selecting a few events from the same discipline of the sport. But there are cases where accumulator bets are made from events from different sports.
Read this article if you want to know more about accumulator bets.