Christus Victor is a fancy way of saying that Jesus won a big battle against bad things like sin, death, and the devil. It's like playing a game where the bad guys are really strong, but then the hero comes in and defeats them all.
So, a long time ago, people did some bad things and made God upset. God wanted to help us and make things right again, but the bad things were too strong for us to handle on our own. Then Jesus came along, and he was like the super-strong hero who could defeat all of the bad things.
Jesus did this by sacrificing himself on the cross, and then he rose up again three days later, showing that he had power over death. This made it possible for us to be forgiven and saved from the bad things, so that we can live happy and good lives.
So, when we say "Christus Victor," we're celebrating how Jesus saved us and won the battle against the bad things, like a hero defeating a dragon or a superhero saving the day.