The long-term partner and now second wife to the current Prince of Wales, and his mistress during (part of?) his marriage to Diana, prompting her famous interview comment that there were three people in the marriage. On 10 February 2005 it was officially announced she and Charles would marry on 8 April in Windsor; this was delayed to the 9th when it clashed with the Pope's funeral. She is henceforward styled HRH The Duchess of Cornwall, but not Princess of Wales; and on Charles's accession she will be known as Princess Consort, not Queen.
Mrs Parker Bowles was for a long time not proper company in the eyes of the Royal Family, though very gradually after Diana's death she has emerged and been seen in official company with him, spent time with his sons, and so on. She met The Queen in 2001. With the huge wave of sympathy for Diana her position was impossible, but now that years have passed, most of the country will accept the future King Charles's marriage to her. Opinion polls are generally in favour, though not by a huge amount, though are very strongly against her being called Queen. But she is divorced with a husband living, so parts of the Church of England would have severe problems countenancing remarriage, considering that Charles will become the head of the church on his accession. However, the Archbishop of Canterbury has approved their marriage.
By the time that happens, both church attitudes to divorce and the disestablishment of Church and State might be more advanced. Until the announcement of their engagement it was not clear whether we could one day expect a Queen Camilla. The alternative possibility, of a morganatic marriage whereby she becomes his wife but not his queen, had been dismissed as contrary to English law and custom. The styling of the King's wife as Princess rather than Queen has not happened before in Britain, but is paralleled by the husbands of Queens Anne, Victoria, and Elizabeth II being styled Prince rather than King.
Camilla Rosemary Shand was born at King's College Hospital, London, on 17 July 1947. In the paternal line, her father was a major, grandfather an author, great-grandfather a writer and barrister, all eminently respectable. The other side is both more noble and more interesting, because of one particular lady's naughtiness with a Prince of Wales a hundred years ago.
Her mother's father was the 3rd Baron Ashcombe. In 1920 he married Sonia (b. 1900), the daughter of the Hon. George and Alice Keppel. And Alice Keppel was the mistress of the Prince of Wales, later King Edward VII. It was quite the scandal, or at least gossip, of the day. So, depending on when that relationship occurred (the DNB says it began shortly after their meeting in 1898), it is quite possible that our Camilla is the aunt twice removed of Charles. In any case, even if there is no royal and illegitimate blood to be sniffed out in her veins from that, George was the son of the 7th Earl of Albemarle and Alice née Edmonstone was the daughter of a 4th baronet.
Eleven generations back comes King Charles II by his mistress Louise de Kéroualle. The complete genealogy has been assembled at http://members.aol.com/eurostamm/camilla.html. Here you'll also find, in brief, how she's related to Diana, how by the legitimate line to Charles, and to a few other interesting names: Henry David Thoreau, Celine Dion, and Madonna! Oh, and by the way, Alice's sister Violet Keppel (later by marriage Violet Trefusis) was a lesbian lover of Virginia Woolf.
Back from the past to Camilla herself: she married Andrew Parker Bowles at the Guards' Chapel in Wellington Barracks, London, in 1973, and they divorced in 1995. They have two grown-up children, Tom and Laura. The surname is often seen as hyphenated Parker-Bowles, but the royal website and the BBC give it as two words.
She's a little over a year older than Charles. They met at Windsor in 1970, when they were both in their mid twenties. A famous picture of them together shows her as quite pretty, and sweet, I've always thought, caught with the Prince in a sort of intimate but innocent moment. These days no-one would call her anything much but horsy, but they're getting on, for heaven's sakes!
There is quite a good summary at http://www.hellomagazine.com/profiles/camillaparkerbowles/, but I simply refuse to quote Hello! magazine.