Sometimes, during a League of Legends match, it happens to see on screen and heard a message that says a particular champion did an ace. But what does it mean?
An ace occurs when the last player of the opposing team dies. It means that all 5 of them are dead at the same time, whether it be for 1 second or much longer. The ace is attributed to whoever scores the killing blow on the last champion to die, although there is no extra bonus for it.
If you get an ace during a team fight in late game, usually you can push and win the game right then and there. Other times, you get an ace by killing their lone defender right before the other 4 of them spawn, in which case it's less meaningful.