Oddly, not the Platonic Ideal of the philosopher (although in fairness, he would have been the first to point that out), Plato is one of the trio of great Greek philosophers who helped to define Western Philosophy and Science for millennia. The other two were his mentor, Socrates, and his student, Aristotle (who was himself the teacher of Alexander the Great).
Plato was born in Athens (although the exact date is unknown – the one I have used here is traditional, but not necessarily correct) to a wealthy family, and given the best education money could buy. Even as a child, he was known for his quick mind. As a younger man, he traveled widely in search of knowledge, and returned to Athens at the age of forty to found the Academy, an institution that would last for nine centuries and train many philosophers, scientists and others from all over the ancient world.
He also left behind a considerable body of writing that helped to define the parameters of philosophy and science until virtually the Renaissance. He also wrote on politics, art and religion. Often, his writings were in the form of Socratic Dialogues, in which Socrates would be the one who espoused the ideas that were actually Plato’s.