Knight

Knights were members of the noble class pledged to the king's (or emperor's, as the case may be) service as military officers or members of the cavalry. Being relatively wealthy and members of the noble classes, knights were generally the best trained and best armored of the fighting classes.

Becoming a knight was part of the feudal agreement. In return for military service, the knight received a fief and a noble title. Knights were addressed as "Sir [name]", and they were usually granted noble arms to make them more identifiable while in armor on the battlefield or in tournament.

Becoming a knight
The earliest knights were simply armored cavalrymen, but by the onset of the High Middle Ages, the chivalric class had become cemented as an essential institution of feudal society. By this time, there were only a few ways in which a person could become a knight. The first way was the normal course of action for the son of a noble:

When a boy born of the noble class was about eight years old, he was sent to a nearby knight to be trained as a page. He spent most of his time performing menial tasks, but also physically training. He learned how to fight with a spear and a sword, practicing against a wooden dummy called a quintain which, when hit, would spin around quickly often hitting the trainee. The young man was also taught reading, writing, music and dance, as well as courtly etiquette.

Around the age of fifteen or sixteen, a page could become a squire in service to his knight. The squire's duties often included maintaining the knight’s equipment as well as completing advanced training. He followed the knight to tournaments and assisted his lord on the battlefield. Upon reaching adulthood, a squire could become a knight after proving himself capable of the duties worthy of the honor of the title, if the king decided to grant him the title. The night before the ceremony, the squire would dress in a white linen tunic, and he would fast and pray all night for the purification of his soul. The chaplain would bless the future knight's sword and then lay it on the altar. When dawn came, the priest would hear the young man's confession, a Catholic contrition rite. The ceremony took place in front of family, friends, and nobility. The squire knelt in front of the lord, who tapped the squire on each shoulder with his sword and proclaimed him a knight. Some knighting ceremonies may have included a forceful strike, knocking the new knight off his feet.

A young man could also be granted knighthood for extraordinary valor in combat.

Chivalry
Knights were expected to adhere to a strict moral code called the code of chivalry, though the specific tenets of this code evolved over time. Early on, chivalry was strictly a military code of conduct, dictating loyalty above all. Eventually chivalry evolved to imply not only loyalty, courage, valor and courtesy, but also defense of the weak, defense of women's honor, and service to God at all times. The code of chivalry did not extend to the lower classes, and 'the weak' was widely interpreted as 'noble women and children'. Knights often treated common folk coarsely with impunity, as they were members of the nobility.

Armaments
The medieval knight was among the most heavily armed members of the military, often depending on squires to keep his armor and weapons clean and in good working condition. A knight's main weapons were his sword and lance, though they may have also trained with a variety of weapons. Early medieval knights wore chainmail armor, which was heavy, uncomfortable, and difficult to move in. As time passed, knights covered their bodies with steel plates, covering their chests, back, arms, and legs. Suits of armor were hot, uncomfortable, and heavy to wear. Some knights even protected their horses in armor.

Knights often used handheld shields for personal defense during battle. These were usually partly or entirely made of wood and often painted with their coat of arms. This practice started around the 12th century as a way of identifying each other on the battlefield, beginning with bold colors and simple totemic symbols, but these soon became far more complex, giving rise to the science of heraldry.