The House of Lords is a house of the British Parliament, formed of the hereditary Lords Spiritual and Temporal of the Realm. The official name is the Right Honourable the Lords Spiritual and Temporal of the United Kingdom of Great Britain and Ireland in Parliament assembled.
The House of Lords evolved from the "Great Council" (Magnum Concilium) that advised the King from 1066, during the reign of William I, to the first convention of the Parliament in 1295. This advisory council was formed of clergymen, aristocrats, and representatives of the counties of England and Wales. The first technical session of Parliament was known as the "Model Parliament," and was held in 1295. It included Archbishops, Bishops, abbots, earls, barons, and representatives of the shires and boroughs.
It wasn't until the reign of Edward II (1307-1327) that the House of Lords had gained absolute supremacy over both Crown and what was then known as the House of Commons, which was formed of the representatives of the shires and boroughs.
In the reign of Edward II's successor, Edward III, the two houses of Parliament both had clearly-defined chambers in which they were to meet; the House of Lords had the White Chamber, and the House of Commons had St. Stephen's Chapel.
Fulfilling other roles, the House of Lords also has roles in the judiciary, serving as Lords of Appeal in Ordinary.