Well kiddo, have you ever heard about a special bond between two things or people? That's what a relationship is! And Coomber's relationship is just a fancy way of saying a special bond between Coomber and someone or something else.
Just like how you have friends or family members that you love and care about, Coomber can have special relationships too. It could be with another dog, a human, or even a favorite toy!
Sometimes, Coomber's relationship might change over time as he meets new people or experiences different things. But that's okay, because relationships can grow and change just like we do as we grow up.
So, in short, Coomber's relationship is just a special connection he has with someone or something important to him, just like our own relationships with our loved ones.