Leader (max. 1)
A senior flag officer, and the leader of a faction. Leaders have the ability to demote/promote any member. They can kick any member from the faction, and they can even resign. A leader is in charge of keeping the faction in order and coming up with rules for the faction. The main job of the Leader is to determine the course of the guild, and to create harmony between her members.
Director (max. 1)
A flag officer, and essentially the leader's second-in-command, the director is usually a person who is trustworthy and a good friend (either in-game or IRL) of the leader. They will often enforce the rules, and basically just run the faction when the leader is not around. The director can promote/demote, and kick from the faction any member except the leader. They can add people to the faction, grant titles, and change the faction slogan (which the leader can also do). There is only one director and one leader for any faction.
The main job of the Director is to assist the Leader, and to serve as a deputy when the Leader is offline. A Director can appoint Marshals to manage certain subtasks.
Marshals (max. 4)
Marshals are Veteran Officers who can promote Commissioners and can demote Executors. They can also add people to the faction. Marshal are the eyes and ears of the Director/Leader. Their main job is to control the flow of members, and to maintain order within the guild. They have several Executors beneath them.
Officers, with one ability, the ability to add people to the faction. They work under supervision of a Marshal. The max number a faction can have is 12 executors.
This is the lowest rank of a faction. Most players who are member of a guild are Commissioner.