In the 20th century, historians grouped society into a set of ranks and responsibilities:
|King||Ruled and protected the country.|
|Barons||Given high rank by the king who had land and power.|
|Knights||Fought for the king and country.|
|Peasants||Did all the work, like farming.|
All medieval people did homage, a promise to be loyal, to their 'lord' and there were no rules or restrictions on the power of the king.
William the Conqueror, one of the kings in the Middle Ages, created the Domesday Book (1086). He sent officials all over England to assess and value the wealth of the land and who owned it. The Domesday Book shows medieval society was much more complicated than this, and historians nowadays do not believe that the 'feudal system' ever really existed.
The idea of the 'feudal system' does still provide a good starting point for your study of Britain's government.
In theory, the government of William the Conqueror was 'absolute' – he owned all the land, ruled all of the people and did whatever he wanted. Over the next millennium this absolute authority was challenged and defeated. Britain chose instead a system of government where power goes bottom-upwards from the people to Parliament, who make the laws, rather than top-down from the king to the people.