Chivalry refers to the medieval institution of knighthood, and most especially the ideals of knightly virtues, honour and of courtly love.
The word comes from the French word, "chevalerie", which means "skills to handle a horse". The word comes ultimately from the Latin caballus, or "nag". (This word developed into the term for "horse" in languages descended from Vulgar Latin.) The French chevalier, the Spanish caballero, and the English cavalier derive their names from the same word. The ability to handle a horse, especially in combat, was of utmost importance to a medieval knight. As the Middle Ages progressed, the term "chivalry" began to take on new meanings. The intention, in all these cases, is to distinguish the aristocratic knight on horseback from the peasant infantryman walking with his pike and the artilleryman dragging his vulgar machinery.
In war, the chivalrous knight was brave in battle, loyal to his king and God, and willing to sacrifice himself. Towards his fellow Christians and countrymen, the knight was to be merciful, humble, and courteous. Towards ladies above all, the knight was to be gracious and gentle. The idealized relationship between knight and lady was that of courtly love.