Court in this case would mean the sovereign (king, queen, whomever) and the people surrounding them. The court was, in some ways, the adminstrative heart of the ruler's country. The ruler would be surrounded by advisors, bodyguards, people who had business with the king, nobles, retainers (people who were "retained" in the service of a person), or sometimes even people the ruler had just taken a liking to. In a court you could find figures like the steward (someone who helps the ruler govern), a chaplain (a religious person who was basically assigned to the court), or military men. When nobility and monarchs became less crucial in the running of governments, the court became less crucial as well. Feel free to ask if you have any more questions or correct any errors I may have made.