It's about being a man on a horse delivering letters or something. I thoroughly recommend it.
Actually I think he might be picking letters up from the ground. Which is a bit weird because we don't usually pick up letters from the ground unless someone's dropped them. Which leads me to believe that another postman really messed up. Maybe there was a hole in his letter bag. Maybe he was having a bad day and decided to just throw all the letters out of his bag instead of delivering them. We've all had days like those.
Anyway, this is fun. Check it out.