Wales is one of the constituent countries of the United Kingdom, and sometimes referred to as a Principality, although the Welsh Assembly Government say this is not correct.
The Anglo-Saxon invasions that led the the emergence of England did not penetrate into Wales, which therefore remained independent, different parts being rules by different kings (including Maelgwn, King of Gwynedd) and princes.
King Edward I, having conquered Wales, is said to have offered the people of Wales a prince who spoke no English, and fulfilled this promise by prsenting to them at Caernarfon his son, the future Edward II, who was still a baby. Since then the title "Pirnce of Wales" has been regularly granted to the eldest son of the monarch.
For most purposes, England and Wales have been treated as a single unit in legislation.Since 1999, Wales has had its own Assembly, although its powers have been less than those of the Scottish Parliament.