Okay, so you know how some people are born into families that have a lot of money and power? Well, in Mongolia a long time ago, there were also people like that, but they were called the nobility.
The nobles were like the bosses of their own areas, and they had a lot of land and animals and other things that made them rich. They also had many people working for them, like farmers and soldiers.
The most important noble was the king or the "Khan". He was kind of like the big boss of all the other nobles. He made the big decisions and had a lot of power.
The nobles usually wore really fancy clothes and had a lot of cool things in their houses, like beautiful carpets and furniture made of gold and silver. They even had their own special language that only they could speak called "Classical Mongolian".
However, the life of a noble wasn't always easy. They had to work hard to keep their power and protect their land from other nobles who might want to take it away. They also had to deal with wars and other problems that would come up.
Some of the most famous Mongolian nobles were Genghis Khan, who was one of the greatest conquerors in history, and his grandson Kublai Khan, who ruled over China.
So basically, Mongolian nobility was a group of really rich and powerful people who had a lot of land, people working for them, and cool things in their houses.