Question: what is the difference between royal highness and royal majesty?
Answer: HM (Her/His) is the third-person form of address to a Queen or King, it is above any forms of address. Royal Highness (Her/His/Your) is used to address members of royal family, usually Princes and Princesses. Majesty is normally the style or manner of address for a king and queen so putting 'royal' is redundant.