A traffic light is a thing you see on the road with three different colors - red, green and yellow. It is used to make sure that the cars, trucks and people walking on the road can move safely without crashing into each other.
When the traffic light is red, it means you must stop. This is like when you play red light, green light game with your friends. You must stop walking or running when the person shouts “red light!”. But, in the case of the traffic light, cars and other vehicles must stop when it shows red, because it is their turn to wait.
When the traffic light shows green, it means it’s okay for you to go. Just like your teacher tells you to, "Go ahead, it's your turn to speak or answer." It means it's your turn to move forward. When you see the green traffic light, you can go ahead safely.
Finally, when the traffic light turns yellow, it’s like a warning. It means it is about to turn red and you must be prepared to stop. It’s just like when your mom tells you, "be ready, the dinner will soon be ready" or "your favorite TV show will begin in 5 minutes". It means get ready for a change.
So, a traffic light is like a sign that tells cars and people when they can go and when they must stop or wait. It keeps everyone safe, like rules in a game, and helps us get where we need to go without crashing into each other.