Issue #1 of Knight Life
A knight is essentially a mounted warrior in the service of his liege-lord.
The mounted warrior had a great advantage on the battlefield. Using the speed and momentum of a charge, the horse could trample his rider's enemies; the rider could use the long lance to injure his foes while he remained out of reach of their weapons. Then, with all speed, the knight could ride off, only to return for another deadly attack. This technique had the most devastating effect when the cavalry worked together in formation. The horse-mounted soldier was therefore of great significance to an army's leaders; thus the root of the French word for knight, chevalier, is the French word for horse, cheval.
The ability to wield a sword or lance from horseback was a special skill that took practice and wherewithal, and it also took practice with comrades to learn to work together as a team. A lord would employ knights and give them the time and equipment they needed to practice; in return, they served their lord as vassals. The duties of a vassal could include not only fighting in his lord's army, but guarding his castle, giving him financial aid, acting as his messenger or ambassador, and serving on his council. The knight was under his lord's protection, both legally and militarily.
It was the relationship between himself and his lord that defined the knight's life. The lord's position gave him considerable control over the knight's life, career, and future, including the final say in whom the knight could marry and the disposition of his estate after his death. The lord technically owned the land used by the knight to raise revenues, and while the property usually remained in the knight's family for generations, it was the lord's prerogative to revoke a knight's right to the land and give it to someone else.
A lord might also be a knight in the service of a higher authority, who in turn would serve his liege, all the way up to the king. This chain of service was the basis of feudalism, and its importance is revealed in the Saxon word for servant, cniht, which gives us our English knight.
Today, the word "knight" conjures up far more than war and service. Loyalty, courtesy, honor, glory, courage -- all this and more come to mind when we think of the knight in shining armor. And, indeed, as history unfolded, the knight's role in society altered from that of a cavalry soldier to a model of behavior. Yet, as we know, knights were only human, and did not always live up to the standards imposed on them by society.
Check out Issue #2 of Knight Life: The Origins of Knighthood in Europe:
http://historymedren.about.com/library/weekly/aa031398.htmView the Knight Life Table of Contents:
http://historymedren.about.com/library/blknighttoc.htm 
