The Magna Carta only gave rights to "free" people. Who was not free in Medieval England?

In England, during the Medieval ages, from the end of the 5th century through to the start of the Early Modern period, the Society was similar to a pyramid. At the top of was the king, below the barons, also known as tenants-in-chief, who were granted land from the king in exchange for providing soldiers to fight for the kingdom. Similarly, the barons granted land to knights, who In return had to fight for a number of days a year.

At the bottom of this Medieval Englan society were farmers, who were not free and besides working on their own land they had to work the lord's land several days a week and could not leave their land without the lord's permission.