Okay, so imagine a really big kingdom a long-long time ago in a place called Iran. In this kingdom, there were different groups of people who ruled over different parts of the land.
One of these groups was called the "Alid dynasty" and they ruled over the northern part of Iran. Think of it like a big puzzle, and the Alids were one of the pieces of that puzzle that made up the whole kingdom.
The Alids were named after a man named Ali, who was really important to the Muslim religion. People who followed Ali's teachings were called "Shia Muslims" and they thought that Ali should have been the leader of the whole Muslim community instead of someone else named Muawiya.
The Alids were really good rulers and they helped their people a lot. They had a lot of wise leaders who made sure that the people were safe and happy. They also built many important structures like bridges, schools, and libraries.
Eventually, the Alids lost their power and the kingdom was ruled by different groups of people. But even today, people still remember them as one of the great dynasties of Iran's history.