Please explain

In the middle of a treatment the other day, the kid's mom asked me, "Are you Catholic, Protestant, or Presbyterian?". Apparently I appear to be a type of Christian. After I told her I was Catholic, she asked the child to ask me his question. The burning question, "What is a saint"? I guess he was interested since he had been to some Caribbean islands. So I did my best simple explanation of what a saint is to the young one, and he seemed satisfied with the answer.