Prince of Wales
Prince of Wales is the title given to the male heir to the British throne, having been instituted by King Edward I for his son, the future Edward II which legend tells us was at Caernarvon Castle in 1284, but was in reality at Lincoln 17 years later. Currently, the eldest son of Queen Elizabeth II, Prince Charles, holds the title. These days the office has no administrative function, and is purely honorific.
By law the wife of the Prince of Wales is titled the Princess of Wales. Prince Charles's first wife, Diana, Princess of Wales, held the title from her marriage, and continued to hold it after her divorce until her death. When Prince Charles married for a second time, there was some debate as to whether his new wife Camilla would be entitled to the style. The Lord Chancellor reviewed the case and determined that unless there was a legislative change, the wife of the Prince of Wales was automatically the Princess of Wales. Camilla, while legally the Princess of Wales, however chose not to use the title Princess of Wales, but instead Duchess of Cornwall, which is a title held concurrently by all Princesses of Wales. If Charles ascends to the British throne, Camilla will legally be titled Queen Consort but she has indicated that she will rather go by the honorific Princess Consort. Female heirs to the throne in their own right are not legally Princesses of Wales.
The name "Wales" is often used by the Prince of Wales and his family as a surname.