Okay kiddo, so you know what a marathon is right? It's a really really long race that people run over 26 miles. Now, there's a special kind of marathon called the "man versus horse" marathon.
In this marathon, people run against horses, just like the name says. And because horses are really fast and strong, people have to try extra hard to keep up with them!
So some people will run the marathon on their own two feet, while others will ride on horses. And they all try to finish the race as quickly as possible.
Now, you might be wondering, "why are people racing against horses?!" Well, it's all just for fun! It's a way for people to challenge themselves and see who's faster, humans or animals.
But here's the catch: sometimes, people actually win! That's right, some people are so fast that they can outrun the horses! Of course, it doesn't happen very often, but it's still really cool when it does.
So there you have it, a man versus horse marathon is a really long race where people run against horses just for fun. And sometimes, people even win!