The term "Philosophy" means "Love of Wisdom" in Greek.  Wisdom is more than knowledge.  It may include things like being able to apply one's knowledge or having a deeper understanding of information, or having common sense, but it certainly also includes understanding the limits of one's knowledge.  One of the first philosophers who understood this distinction was a Greek named Socrates.  The Oracle at Delphi told Socrates' friend that Socrates was the wisest man alive.  Socrates was confused, because he didn't feel that he knew very much, if anything, but he did have faith in the oracle.  He decided to try to find someone who was wiser than he was, and he began to travel around the country speaking to those who claimed to be wise.  He found that every single one of them thought he knew things, but was unable to answer all of Socrates' questions clearly or completely.  He concluded that he was the wisest man because, even though he didn't know much, he was at least aware of that fact, unlike others, who thought they knew a lot but were mistaken.

As modern philosophers, we strive to meet the challenge presented by Socrates.  We only accept as true those things which we completely understand and for which we have sufficient evidence.  Philosophers have succeeded in many areas:  they have discovered the Laws of Nature in physics, they have come to understand the chemical connections between elements, they have developed mathematical tools including calculus, and they have uncovered the genetic foundation of all life, among many other things.  As you can see, all fields of study, Physics, Chemistry, Biology, Mathematics, and every other science are divisions of philosophy.  Any attempt to discover the truth is philosophy.

One might ask, then, what distinguishes the study of Philosophy from all other studies.  Generally, the sciences deal with a specific subject matter, where a core set of truths have been uncovered which are universally accepted by all experts in the field.  The academic study of philosophy deals with those questions which are not dealt with in any other field.  The questions in philosophy are those which are difficult to answer, and for which there is no universal consensus on the right answers.  The study of philosophy is often broken down into several categories including metaphysics, epistemology, theology, and ethics.  Other fields which fall under academic philosophy are aesthetics, social/political philosophy, and logic or reasoning.