In medieval Europe, the swearing of fealty took the form of an oath made by a vassal, or subordinate, to his lord. "Fealty" also referred to the duties incumbent upon a vassal that were owed to the lord, which consisted of service and aid.
One part of the oath of fealty included swearing to always remain faithful to the lord. The oath of fealty usually took place after the act of homage, when, by the symbolic act of kneeling before the lord and placing his hands between the hands of the lord, the vassal became the "man" of the lord. Usually, the lord also promised to provide for the vassal in some form, either through the granting of a fief or by some other manner of support. Typically, the oath took place upon a religious object such as a Bible or saint's relic, often contained within an altar, thus binding the oath-taker before God. Fealty and homage were key elements of European feudalism.
Fealty is distinct from other parts of the homage ceremony, and is usually used only to refer to that part of the ceremony where the vassal swore to be a good vassal to his lord.