The knight is set apart from the other members of the kingdom. They are representatives of the king. His elite fighting force.They report only to him. Though they may hold lands and titles they are above any noble. A knight represents the best of the best, a role model. They server as the generals in the kings armies and under take his personal quest.
Answer only to the king.
May not be taxed by nobles.
Have access to the Royal Armoury.