Imagine you have a toy that someone else wants. They can't just take your toy because that would be wrong, but they can ask someone in charge (like a teacher or parent) to decide who the toy belongs to. This is kind of like a court case.
Now, imagine you have a toy that someone else wants and they take it from you. But they don't just take it, they also hurt you by taking it. You can go to the teacher or parent and ask them to not only decide who the toy belongs to, but also to punish the person who hurt you. This is kind of like a quasi in rem case.
In legal terms, quasi in rem means a court case where someone wants to take control of property (like your toy) but the case also involves punishing someone for doing something wrong (like hurting you). It's not just a regular court case about property, it's a special one that also involves punishing bad behavior.