The document defines key terms from the Middle Ages, a period in European history from around 500 to 1500 AD. It describes the feudal system of land exchanged for military service, with nobles providing knights land and knights protecting nobles. It also mentions the Black Death plague that killed millions between 1347-1351, William the Conqueror who became King of England in 1066, and Joan of Arc, a teenage girl who led French troops in the Hundred Years War.