Okay kiddo, have you ever heard of a race called the marathon? It's a really, really long race where people run for 26.2 miles! Now, some countries keep track of how fast their runners can finish this race, and those are called national records.
For example, let's pretend you live in a country called Lemondrop Land. If a runner from Lemondrop Land finishes the marathon faster than any other runner from your country has ever finished before, that runner will now hold the national record for the marathon in Lemondrop Land.
It's like a big achievement for that runner and for the country too, because it shows that Lemondrop Land has some really fast runners! And when people break national records, they might even get special recognition or prizes for doing so.
So basically, national records in the marathon are like a way to keep track of how fast runners from different countries can go in that really long race. Pretty cool, huh?