As you travel around, you will note that there are several kingdoms in the game besides England and France. These two kingdoms are the largest and best organized in Europe and their kings have more powers than other kings. The other kingdoms, in addition to being smaller, are less permanent. Few of them survived into the modern period.
The first letter of the fief code indicates which kingdom you are in. Below are the one letter codes for kingdoms:
A Arles Formed from the ancient Roman provinces of southern France (Narbonesis, etc) and named after its capital, Arles. While technically a kingdom, and one with a pedigree exceeded only by France, Arles was very much in the shadow of France and was dominated by the French king. Often referred as the Arleate.
C Catalonia An area in north-eastern Spain that has a unique dialect of Spanish and is, to this day, still distinct from the rest of Spain.
E England In this period, consists only of England and the recently conquered Wales. Scotland did not join England, to become Great Britain, until the 1700s.
F France Somewhat smaller than modern France. Arles was an independent kingdom and the areas bordering the Rhine river and Italy were also independent.
G Naples Basically southern Italy. The boundaries constantly shifted with the ups and downs of local politics.
H Holy Roman Empire (or parts of it) Originally the area put together by Charles the Great (Charlemagne) in the 8th and 9th century. It then consisted of France, most of Germany and parts of Italy, Austria and Spain. In the 14th century it was more of a loose confederation whose Emperor was elected by the great magnates ("Electors") whenever the current emperor died.
I Italy A kingdom in name only, as no one was able to unify the many independent parts of Italy until the 19th century.
L Leon-Castille The central part of Spain and, eventually, the core of a united Spain in the late 15th century.
M Mallorca A group of islands off the coast of Spain, plus some bits of property on the mainland. Later absorbed by Spain.
N Navarre For the most part, the Basque speaking regions of north-west Spain and south-west France. Eventually gobbled up by Spain and France.
R Ireland Conquered by England in the 12th century, the throne was held by the king of England until the 1920s, when part was kept in the United Kingdom and the rest became, for the first time in 800 years, an independent Ireland.
S Scotland Basically the same land that now comprises modern Scotland, but sharing a long term uneasy relationship with England.
All of these kingdoms are much less significant than England and France, which were the two most powerful kingdoms of the time. Some kingdoms will be referred to as part of the Holy Roman Empire, this was also an insignificant political entity.