Who were they?

Feudal lords were the ones who controlled the land on which cities were built. The vassal was independent of the lord. He swore loyalty to the lord, help and advice. The lord had to protect his vassal give him the resources he need to survive , it was usally a fief , which was land.

A noble could be a vassal of the king , and in the same time he could also be the lord of a lower social rank.
Religious people could also be feudal lords , because the received fiefs.      
                

 During the  1100, certain men  had castles and courts that rivaled the king's; there could be serious threats if they were not happy in their dealings with the crown.
                    
                             

In 1215, the English barons formed an union that obligated King John to sign the Magna Carta. While it gave no rights to ordinary people, the Magna Carta did limit the king's powers of tax and require trials before punishment. It was the first time that an English monarch came under the control of the law.