A feudal baron is the lowest ranking land-owning noble in the feudal system. The baron's fiefdom is called a "barony". The baron serves directly under a Count. Not many counties are large enough that the count feels the need to separate them into baronies and appoint barons, in which case the county is ruled directly by the count. The baron is to the count what a count is to a duke. He has the same responsibilities to the count as the count has to his duke.
A baron is selected by a count from local nobles, or given a noble title in order to serve as baron over one of the count's baronies. Usually the candidate is selected based on friendship, political clout or service to the count.
A baron is responsible for managing the fief that he has been given by his count. This means that the baron is more directly responsible for taxing the serfs and making sure that they fulfill their feudal duties. A baron may not appoint lower ranking nobles to rule over parts of his land, but he can appoint magistrates and sheriffs to manage law and order in the fief. Should the count be mustered to battle by his oath of fealty, the baron is required to join the count in battle. A baron generally does not have any knights in his service, and are generally not knighted himself. Instead he relies on paid soldiers to keep the peace.