Socrates was one of the most important philosophers in western history. Through Plato, his views on ethical questions have had a lasting influence on how Philosophy is taught and conducted in modern universities.
The Greek Oracle had claimed "No one is wiser than Socrates" which puzzled Socrates as he professed to know nothing. By logical discourse he would argue opponent's definitions were inadequate and that they must continue the search for an ideal definition of the discussion's topic.
Socrates was often used by Plato as a mouthpiece to represent Plato's own philosophical viewpoints. As Socrates didn't write anything down it is principally through Plato's writing that the picture we have of Socrates is taken.