Okay kiddo, do you know what a bridge is? It's something that goes over a road or river so people and cars can go from one side to the other. An overpass is like a bridge, but it goes over a road or highway specifically.
Sometimes, there are too many cars on a road and it gets really crowded. That's why we have overpasses - they help to ease traffic by allowing cars to drive over the busy road instead of waiting at a stoplight. This way, cars on the overpass can keep moving, while the cars on the road below can keep moving too.
Overpasses can also be used to help people cross highways safely. They have sidewalks or paths for people to walk, so they don't have to cross a busy highway with cars zooming by.
So in summary, an overpass is like a bridge that helps people and cars go over a busy road or highway. It's there to make things easier and safer for everyone!