Fawkes, the
phoenix, is
Albus Dumbledore's
familiar or wizard pet.
According to the Harry Potter series, phoenixes are songbirds with some very useful properties like the ability to carry a large amount of weight, and tears with healing powers.
Their tail feathers are sometimes used in the cores of magic wands. Fawkes gave two tail feathers to Mr. Ollivander for making wands that were subsequently purchased by Voldemort and Harry Potter.
Fawkes first appears in the series in the second book: Harry Potter and the Chamber of Secrets in Albus Dumbledore's office. He seems to be at the end of his life cycle (burning day) and spontaneously combusts before rising again, newborn, from his ashes.