Ex:If a peasant is traded into farm and land work for protection plus a portion of the harvest, instead of money.
There is no central governments, instead, lords of smaller units of land control the warriors and peasants.
These lords owe obedience to a distant weak duke, king, or emperor.
In Japan and Europe, constant warfare which makes warriors a important class in both the places.
These were called "samurais" in Japan. Japanese samurais used lecquered leather or metal plates and silk or metal binding. This armor would help their movement speed but wouldn't give the that much protection.
These were called "knights" in Europe. Knights used all metal, made of chain mail or metal plates. This type of armor would limit their movement speed but would have them extremely protected.
Feudal lords built different things, Europeans lords built stone castles to protect themselves and their vassal. Although Japanese built castles, they were made of wood not stone.