Short answers, pulled from the story.
Plato was an ancient Greek philosopher of Classical Athens, most commonly considered the foundational thinker of the Western philosophical tradition. He was an innovator of the literary dialogue and dialectic forms and the founder of the Academy in Athens. Alfred North Whitehead said European philosophy consists of a series of footnotes to Plato.
Plato was born between 428 and 423 BC into an aristocratic and influential Athenian family. He died in 348 or 347 BC and was buried in his garden in the Academy in Athens.
Plato's Theory of Forms denies the reality of the material world, treating it as only an image or copy of the real world. It holds there are two kinds of things: the changing world of material objects grasped by the senses, and an unchanging, unseen world of Forms grasped by reason. The theory is first introduced in the Phaedo dialogue.
Plato's teacher was Socrates, his greatest source of inspiration, who appears in every dialogue except the Laws. His most famous student was Aristotle of Stagira, who arrived at the Academy in 367 BC and became a philosopher as famous as Plato in his own right.
The Academy was the philosophical school Plato founded near the sacred olive grove of Hecademus in roughly 383 BC. It began as only a house with a garden, and Plato wrote the majority of his dialogues there. After his death he was succeeded as its head by his nephew Speusippus.
Plato first visited Syracuse around 385 BC when he was about 40, during the rule of Dionysius, whose brother-in-law Dion became Plato's disciple. He returned around 366 BC to tutor Dionysius II toward becoming a philosopher king, and made a third trip in 361 BC, during which Dionysius held him against his will until Archytas interceded.