Okay, so imagine you are a prince or a princess in a big family. In Jordan, the king is like the dad of the family. But if something happens to the king, like if he becomes too sick to be the king or he passes away, then a new king has to be chosen.
The way they choose a new king is based on who is next in line in the family. In Jordan, they follow a rule that says the king's oldest son becomes the new king when the old king can't be king anymore.
But, if the old king doesn't have a son, then it goes to the oldest brother of the king. And if there are no brothers, then it goes to the oldest male cousin in the family.
So basically, when a king can't be king anymore, the next person in line from the family gets to be the new king. It's all about keeping the family together and the country stable.