A roadometer, also known as an odometer, is a special device that can tell you how far you have traveled in your car or other vehicle. Think of it as a little machine that keeps track of every time your car's wheels make a full rotation. Each time the wheels go around once, the roadometer counts it and adds a little bit more distance to your total.
Once your car has gone a certain distance, say 1 mile or 1 kilometer, the roadometer will show you that you've gone that far. It does this by using numbers on a small screen that you can see while you're driving.
It's a really cool tool that helps you keep track of how far you've gone and how much farther you have to go to get to your destination. Sometimes people like to see how many miles or kilometers they've driven in total, and the roadometer is perfect for that too!
So, in summary, a roadometer is like a little machine that can tell you how far you've traveled in your car by counting how many times the wheels go around. It's really helpful for knowing how much farther you have to go on a trip or just for seeing how much driving you do in a certain amount of time.