Magna Carta was originally created because of disagreements between Pope Innocent III, King John, and his English barons about the rights of the King. It required the king to renounce certain rights, respect certain legal procedures and accept that "the will of the king could be bound by law."
The Magna Cart, or "Great Charter" essentially is a peace treaty between John and his barons, guaranteed that the king would respect feudal rights and privileges, uphold the freedom of the church, and maintain the nation’s laws. Although more a reactionary than a progressive document in its day, the Magna Carta was seen as a cornerstone in the development of democratic England by later generations.
The Magna Carta has been subject to a great deal of historical exaggeration; it did not establish Parliament, as some have claimed, nor more than vaguely allude to the liberal democratic ideals of later centuries. However, as a symbol of the sovereignty of the rule of law, it was of fundamental importance to the constitutional development of England. Four original copies of the Magna Carta of 1215 exist today: one in Lincoln Cathedral, one in Salisbury Cathedral, and two in the British Museum.
Learn 6 Things You May Not Know About the Magna Carta at History.com.