A world war is when many countries from all over the world fight against each other. It's like a big fight where lots of people get hurt and many countries get involved.
Imagine if you and your friends from different schools got into a big argument and started fighting each other. You would all be really angry and trying to hurt each other. This is sort of what happened in the world war, except instead of just a few friends, there were lots of countries involved.
One country might start the fight by attacking another country, and then that country's friends might jump in to help them. But then the first country's other friends might also join in, and things would get really complicated.
During the world war, there were two main groups of countries fighting against each other. One was called the Axis powers, which included Germany, Italy, and Japan. The other was called the Allied powers, which included the United States, Great Britain, China, and the Soviet Union.
The world war lasted for several years and millions of people died. There were battles fought on land, in the air, and on the sea. People had to leave their homes and move to other countries to stay safe. It was a really difficult time for everyone involved.
In the end, the Allied powers won the world war, and the Axis powers were defeated. But it took a lot of work and sacrifice from people all over the world to make that happen. The world war was a very sad and scary time, and we should always remember it so that we can work to prevent something like that from happening again.