The term philosophy was probably coined by the Pythagorean school in ancient Greece. It combines two Greek roots, philia (love) and sophia (wisdom). The philosopher therefore is not someone who claims to be wise, but rather someone who loves and seeks wisdom. This term was adopted by Socrates and his follower Plato, to contrast their own pursuit of wisdom for its own sake with the sophists, who claimed to be wise and earned their livings by teaching (selling the wisdom they claimed for profit). In classical antiquity, the term philosophy refered to almsot any possible type of wisdom -- what we call science, for example, in antiquity was considered a branch of philosophy (natural philosophy).
The Stoics divided philosophy into three branches, ethics, logic, and physics, the first dealing with how we ought to behave, the second with how we ought to think, and the third with the nature of the world. Metaphysics, considered part of physics in the Stoic scheme, deals with the nature of being. Theology, which deals with the nature of the divine, is considered a separate, albeit related, discipline.
What is philosophy?
It is the gate way of understanding oneself as Plato, and understanding the metaphysical like saint Augustine. Thank you.