Okay kiddo, so have you ever played a game of tag where you have to run and touch another person to pass them the tag? Yes? Great! Now imagine if your team had more than two or three people and instead of passing a tag, you have to pass a stick.
That's what 4 × 400 metres relay is all about. It's a race where four people, each from the same team, take turns running a distance of 400 metres (which is like running around a big football field). So when one person runs their 400 metres, they pass a stick to the next person on their team, who then runs their own 400 metres, and so on, until all four people have completed their race.
The team that gets to the finish line first, with all four of their runners completing their individual 400 metres, is the winner! It takes a lot of teamwork and practice to make sure everyone is running at their best and knows when to pass the stick to the next person. But it's a really fun and exciting race to watch!