There are many political titles throughout the entire witcher Saga.
Baron
A Baron or Baroness is a vassal of a King or a Emperor. Generally he administer a land (a barony) of hus King, where he must keep the order.
Camerlengo
A Camerlengo is a royal officer, usually the custode of the royal treasure.
Chamberlain
A Chamberlain is a court appointment whose task is to managing a royal household.
Count
A Count or a Countess is generally a vassal of a King or a Emperor. Usually his King gives him a land (a county) where he will rule and keep the order in his place.
Duke
A Duke or a Duchess is usually the ruler of a duchy.
Emperor
An Emperor or Imperator is the highest title in the Nilfgaardian Empire: he's the owner of all the lands, which rules through Counts and Marquises, the tutor of the law and the commander of the Imperial Army, administred though a Field Marshall.
For main article see: Imperator
Lord
A Lord is usually the ruler of a settlement or a little city, and he's a vassal of a King or a Emperor.
Margrave
A Margrave is a political title usually adopted by a military commander whose task is to defend the borders of a kingdom or of a state.
Marquise
A Marquise is a nobleman who have the task of rule over the colonies or his Emperor.
Prince
A Prince or a Princess is generally a child of the currently ruling royal family. If they were the eldest child, they're usually the next in line to become King or Queen.
Seneschal
A Seneschal is a court appointment whose task is to administer the royal house and the servants. Sometimes, he is also a royal officer who must keep the order in the provinces.
Vicerory
Viceroy is a regal official who runs an area (whether it be a city or country) as the representative of a monarch.
Viscount
A Viscount is a vassal of a Emperor. He usually have the task of keeping the juridical order in a province or in a colony.
King
A King or a Queen is the ruler of a Kingdom, where he have the highest authority. He's usually assisted by a royal council and by a Mage advisor.