Jedi Master was the second highest rank a Jedi could obtain, and a traditional requirement for becoming part of the Jedi Council, the main interface between the Jedi and the government of the Republic. It was reserved for those who have shown exceptional devotion and skill in the Force. The title of Sith Lord or Sith Master was on par with the rank of a Jedi Master. Masters act usually for the Order as instructors and envoys for planetary problems. They are the elite forces and most Jedi Watchmen and Advisors are per usual Masters.