Okay kiddo, so the Amman Message is like a really important letter sent to people all over the world who follow the religion of Islam. It's basically trying to get everyone on the same page about what it means to be a Muslim.
See, there are a lot of different beliefs and practices within Islam, and some people might not agree with each other. The Amman Message wanted to clear things up and make sure everyone knew what the "official" beliefs were.
So in 2004, a group of Muslim scholars and leaders got together in Amman, which is a city in Jordan. They talked about all the different beliefs and practices and figured out what was common among all of them. They came up with three things: believing in one God, following the teachings of the prophet Muhammad, and using the Quran as a guide.
Then they wrote a letter, called the Amman Message, to all the Muslims in the world. They said that these three things were the foundation of Islam and everything else was just details. They also said that anyone who believed in these things was a true Muslim and should be accepted by other Muslims.
So basically, the Amman Message is like a big agreement among Muslims about what it means to be a Muslim. It's trying to help everyone get along and see that they have more in common than they might think.