Socrates is known as the father of western philosophy. But in what sense? Is it because there wasn't any other philosopher who preceded him? Or perhaps that their philosophies were completely different from that of Socrates?
Socrates changed how philosophy itself was to be conceived. Rather than a "sophist" ("wise one" - the tag often used for earlier Greek philosophers), Socrates described himself simply as a "philo-sopher" ("lover of wisdom").
Michael Picard makes this point in his Bedside Book of Philosophy:
[Socrates] eschewed rhetorical devices that deceived the audience ... Instead of the 'sophist' tag, Socrates would only lay claim to the more modest term, 'philo-sopher' (lover of wisdom) ... He invited all-comers to join him in inquiry. But the search was the discovery. This is just the process of thinking for oneself."
This point is explored at greater length in this Stanford paper on Socrates.
But beyond this, the title Father of Western Philosophy reflects the influence that Socrates had on the philosophers whose work informed later European thought. Socrates taught Plato. Plato then taught Aristotle. Plato founded the Academy and Aristotle founded the Lyceum - what were, in effect the first two “universities”. The tradition launched there underpinned the future development of Western Philosophy.
In brief (but over-simplified) terms, as to why he is considered a founder of Western philosophy, he lived during the ancient era and Socrates' philosophical ideas have been research/followed by subsequent generation of philosophers. For instance, his descendants are known as the Socratics (the previous link part of Lectures on the History of Philosophy by Hegel) .
In terms of contribution -- ethics, epistemology, politics (cf. Spinoza) -- all are extremely important subject-matters which form the foundation of modern civil society.
If you are really interested, this book traces Socrates' work to modern times: From the Socratics to the Socratic Schools: Classical Ethics, Metaphysics and Epistemology (2015).
Well, in a way, it is debatable as to whether or not Socrates was the Father of Western Philosophy. Chronologically speaking, Western or Ancient Greek Philosophy can be traced back to Thales of Miletus who lived around 600 BC/BCE-(around 250 years before Socrates' time). Thales had the first known School of Philosophy-Science or Science-Philosophy. Other "Pre-Socratic" Philosophers included, Heraclitus of Ephesus, Zeno of Elea, Parmenides, Empedocles, Anaxagoras, as well as Democritus of Abdera-(one could perhaps include, Pythagoras of Samos). Each of these figures made their own significant contribution to the early history of Philosophy, with Thales as its Original Founder.
However, despite this 250 year Pre-Socratic philosophical lineage, the intellectual and rhetorical ingenuity of Socrates does stand the test of time; and when compared with the aforementioned, "Pre-Socratic" Thinkers, Socrates was quite distinct and unique. The major intellectual feature which distinguished Socrates from the "Pre-Socratic" Thinkers, was that the majority of these Thinkers were Philosopher-Scientists or Scientifically oriented Philosophers. Socrates, however, was the first Philosopher-Rhetorician in Western History; that is to say, he essentially invented or pioneered the Art of Conversation, as well as the Art of Debate, both as an expression of wisdom and intellect, though also, at times, an expression of sarcasm, wittiness and haughtiness. Socrates was the constant Conversationalist and Debater-(much to the annoyance of the average Athenian of his time, as well as to the Athenian Government). Eventually, Socrates would convert his public conversational and debating persona into a school-like setting whereby he would meet and educate a number of students, including, a young wealthy man with great intellectual insight named Plato.
So, yes, in a way, Socrates was the Father of Western Philosophy whereby he perfected or refined the art of philosophical argumentation, which has served as the basis of Western style debate-(particularly in U.S., as well as perhaps other Law Schools throughout the greater West for centuries, as well as into the present-day, i.e., "The Socratic Method"). However, one could still make the case that Socrates was not necessarily the Father of Western Philosophy, but that the origins of Western Philosophy predate Socrates by 1-2 centuries.