Okay kiddo, so Saint Stephen was a man who lived a long time ago and was a really good person. He helped a lot of people and taught them about God.
But some bad people didn't like what he was saying, so they got really angry and even hurt him a lot. But even when he was hurt, Saint Stephen still loved God and forgave the bad people who hurt him.
Because he was so brave and good, a lot of people started to believe in God because of him. That's why we remember him as a saint and celebrate his life on certain days.