Okay kiddo, imagine you have a friend who is very sad because they lost their toy. You know that this toy is very important to them and they can't be happy without it. You have a choice to make- you can help your friend look for their toy or you can just ignore their sadness and go play by yourself.
Even though you might want to play by yourself, your heart tells you that it is important to help your friend. This feeling of knowing what is right and what is wrong is called a moral imperative. It's like your inner voice telling you to be kind and do what's right even when it's not easy or fun. Just like when you help your friend find their toy, it's not necessarily something you have to do but it's something you feel like you should do because it's the right thing to do.