Halftime betting is a form of live, in game betting that allows a bettor to place wagers on the outcome of the game at the halftime intermission.
An example of this type of bet came in the first day of the UEFA 2020 European qualifiers in March. Croatia was a heavy favorite (-900) at home against Azerbaijan, but fell behind in the first half before drawing even before the end of the first half.
Everyone watching expected the 2018 World Cup finalists to win the match in the second half. If you were done of them that though that, yo could have bet Croatia at the halftime intermission to go on and win the game at -450. The odds were steep, and you had to lay $450 to win back $550 (your stake plus $100), but the bet ended up coming out, as Croatia went on to a 2-1 victory.