A mixed game refers to a virtual game between two teams. In this bet type you compare the goal difference between two teams that aren't playing against each other, but against two other teams. All bets include the number of goals that are scored at the end of 90 minutes without extra time and penalty shootouts.
For example: Arsenal are playing against Liverpool in the Premier League and Barcelona are playing against Real Madrid in the Spanish La Liga. A mixed game appears as Arsenal vs. Barcelona, even though there is no such actual game.