In Medieval times, a baron was a member of the English nobility. The kings of the era leased land to barons, and in exchange, the barons had to serve on the king's council and provide food and beds to the king and his men when they traveled through the land. Barons also had to pay rent and provide soldiers to the king's army as needed.
Also called the lord of the manor, barons were in charge of their own currency and collecting taxes from the people who lived on their land. They also had their own justice system.
Barons were allowed to use their land however they wished, but they usually gave some of their land to their knights. In some cases, the king required the barons to give land to knights who had fought for the king. The knights in turn gave some of the land to serfs. Serfs had no rights and had to work the land as instructed by the knights.
The present day House of Lords originated with barons serving on the king's council.
In Medieval times, the title of baron was a hereditary honor, but in the middle of the 20th century, the British government began giving out the rank of baron to so-called "life peers" who earn rather than inherit the title.