Roadworthiness is like giving your car a check-up to make sure it is healthy and safe to drive on the road. Just like how you go to the doctor for a check-up to make sure your body is healthy, your car needs to go to the mechanic for a check-up too!
During a roadworthiness test, a mechanic will look at all the important parts of your car to make sure they are working properly. They will make sure things like the brakes, tires, steering, lights, and gearbox are all in good condition. They will also make sure that the car isn't releasing too much pollution into the air.
Think about it this way - just like how you can't play with certain toys if they are broken or dangerous, your car shouldn't be driven on the road if it isn't working properly because it could be dangerous for you and other people on the road. So, it's important to get your car roadworthy every year to make sure it is safe!