The term philosophy comes from the Greek word "φιλοσοφια" [philo-sophia], which means "love of wisdom". Today, it's used to refer to topics such as the nature of existence, what knowledge is, how one should live, etc. Philosophical literature is characterized by its use of reasoning to advance arguments about these topics, to consider competing views, and their difficulties.

Ludwig Wittgenstein once said that philosophy is about letting the fly out of the fly bottle, by which he meant that philosophers aren't in the business of solving problems, but rather of clarifying them. Philosophical analysis, therefore, serves the all-important purpose of making sure we understand what we think, and why we think it, surely a crucial step to make progress in whatever problem is at hand.

Instead of being treated as a single, unified subject, philosophy is typically broken down into a number of specialties (or 'branches') and it is common for contemporary philosophers to be experts in one field but know little about another. Because philosophy addresses complex issues from all facets of life, being an expert on all of philosophy would entail being an expert on all of the most fundamental questions which life has to offer—hardly expected from mere mortals like ourselves.

Below I've listed the various branches of philosophy and offered a brief definition for each. This doesn't mean that each branch of philosophy is entirely autonomous—there is often much overlap between some fields, in fact. For example, political and legal philosophy often cross with ethics and morality, while metaphysical questions are common topics in the philosophy of religion. Sometimes even deciding which branch of philosophy a question properly belongs can cause debate.