Ok kiddo, so you know how sometimes we do things that hurt other people or make them sad? Acts of reparation are things we do to try and make up for those bad things we did. It's like saying sorry and trying to make things better.
Let's say you accidentally broke your sister's favorite toy. You could say sorry and then try to fix it or get her a new toy to make up for it. That's an act of reparation.
Another example could be if you said something mean to your friend. You could apologize and then do something nice for them, like sharing your snack or helping them with their homework. That's also an act of reparation.
Basically, acts of reparation are ways we can show that we're sorry for something we did and try to make things better for the person we hurt.