Socrates focused on asking probing, sometimes humiliating questions in order to learn, Plato believed in immortality of the soul and Aristotle was a champion of reason and believed in avoiding extremes. While the three philosophers had differences, they were more alike as Aristotle was the student of Plato and Plato was the student of Socrates.
Socrates was a philosopher who was frustrated and annoyed with the Sophists at the time. The Sophists in Greece would teach logic and the idea that all things are relative as a way to achieve goals. Socrates believed the truth was more important and that it was the reincarnation of the eternal soul that held all wisdom. This is where Socrates developed what is now known as the "Socratic method," which is asking questions to help rediscover what people knew before birth.
Plato was the prized student of Socrates. He ran the Academy, a place where philosophy was studied. He was both idealistic and rationalistic. He believed in the ideal on one end and the manifestation of that ideal on the other.
Aristotle was the prized student of Plato, though he disagreed with him on several things. Aristotle was a scientist as well as a philosopher. He believed in an "essence" and an opposite of the essence, which he called "matter." He believed matter did not have a shape or a purpose, but essence was what provided that shape or purpose to matter; together they completed one another.