Your majesty is a title of respect for the monarch. "Your Majesty" refers to the steps of the palace. When the emperor was talking to his courtiers, he dared not call the son of heaven directly. He had to call the waiter under the steps to tell him first. Therefore, it is called "Your Majesty", which means to convey the words of the humble to you through the princes at your feet, indicating that the humble speaks to the distinguished.
The word "Your Highness" appeared in ancient books much later than "Your Majesty". Generally speaking, the title of "Your Highness" is used for princes, princes, queens and queens. But "Your Highness" is mainly used for princes and princes. They live in the palace, so they have this title.