Okay kiddo, so do you remember how sometimes when you play with your friends you have to make some rules to make sure everyone is playing fair and nicely? Well, countries around the world also have some rules they agreed on to make sure they all get along and don't fight with each other.
One of the important rules is called the United Nations, which is like a big group of countries that talk to each other and try to solve problems peacefully. Now, inside this big group there is a smaller group called the United Nations Security Council, which is made up of 15 countries.
The United Nations Security Council helps keep the peace and stop bad things happening around the world. They can sometimes decide to use force (like soldiers or weapons) to stop a country or group from doing something very bad, but they have to agree on it first.
So when the Iraq War happened, some countries thought that the Iraqi leader Saddam Hussein was doing some very bad things and they wanted to stop him. The United States, who is a member of the United Nations Security Council, wanted to use force to stop him, but not all the other countries agreed.
Some countries thought that using force was not the best way to stop Saddam Hussein, and that it may cause more problems. They thought the United Nations should try other ways to fix the problem.
But in the end, the United States and some other countries went ahead with the war without everyone's agreement, which caused a lot of controversy and discussion about whether it was the right thing to do.