The Battle of Hastings was fought on 14 October 1066 and the victorious William the Conqueror was crowned the King of England. William introduced a new concept of governance that would last for centuries and what we commonly know as feudalism.
Given the vast size of the country, it was impossible for one man (the king) to rule it effectively, so he divided it into large tracts of land and gave these areas to his loyal men (barons or tenants-in-chief). These barons swore an oath to the king and promised to look after his lands, provide armed soldiers whenever required and share profits with the king. The barons further subdivided the land into smaller portions (called manors) and gave it to knights or sub-tenants. These knights would swear an oath to the baron (and hence to the king) and were sent to the king's service whenever he demanded armed men from barons. The knights also looked after the assigned land, lived in manor houses and shared the profits with the barons. The land was shared between knights, peasants and church.
This hierarchical system of governance is what we know as feudalism and was the result of William's victory in the Battle of Hastings.