I'm guessing this is about the feudal system.
The feudal monarchs (also known as the lords) were the peacekeepers of their vassals. They were the ones who watched over their citizens. People were to believe that the lords were sent by god to rule over them.
The nobles were warriors who'd typically ride on horses. They had to perform an oath to their sovereign; that they'd keep the land safe. They were not paid with money, they were devoted to watching over the vassal.