Albus Dumbledore is regarded by many as the best Wizard ever. He is currently the Headmaster of Hogwarts School of Witchcraft and Wizardry. He is particularly famous for his defeat of the Dark Wizard Grindelwald in 1945, the discovery of the twelve uses of Dragon Blood and his work on Alchemy with his partner Nicolas Flamel. 

Some say that Dumbledore is the only wizard or witch that Voldemort ever feared, and that is why he never attempted to take control of Hogwarts while Dumbledore was in charge. Albus has a pet Phoenix named Fawkes who is very loyal to him. 

Dumbledore most likely knows why James and Lily Potter were killed, but he won't tell Harry until he is ready.