By Prometheus Pyro

As the foundation of all knowledge, philosophy underlies and shapes every other field of thought. There is no physical science or “humanity” which is not inescapably dependent on and influenced by ideas subsumed under the field. Any theory from any subject stands or falls with the philosophical assumptions it necessarily relies on.
Yet this crucial
 subject is widely misunderstood, unknown, and neglected as unserious, unimportant, or uncertain. Looking at what philosophy is and is not should correct these errors.    

What you believe to be true of the basic nature of existence, how you believe knowledge is reached, and how you think you should live are the essentials of your belief system. There are two conflicting approaches to forming a belief system. And there are two opposed resulting kinds of belief systems.

oldest approach to answering fundamental questions is to base beliefs on emotions. It’s inventing supernatural explanations (or, more commonly, accepting those of others). Some form of consciousness is claimed to be responsible for the creation or control of anything someone doesn't want to feel uncertain about. The method of basing belief on emotions is called faith. The resulting kind of belief system is religion. 

Religion was the only approach until the Pre-Socratics of ancient Greece began trying discover (rather than invent) answers to questions about the nature of reality and their place in it. They attempted to look for natural explanations of the world. They sought understanding by studying and reasoning about what they could observe. These early attempts were crude and often absurd by our standards, but they were honest and ground breaking. By taking these first steps with a new approach they created philosophy, a new type of belief system.

Looking at the differences in terms of essentials; it is clear that philosophy is not religion. And religion is, of course, not philosophy. Unfortunately many people confuse the two, often lacking the broader concept of belief system or a grasp of the distinction. There have even been those who have attempted to mix the two approaches. But the existence of such juxtapositions of belief systems does not support the idea that the two are not distinct or opposed. Shaking water and oil together does not prove that water is oil.

Philosophy is also not the particular sciences, nor are they an alternative to philosophy (as some believe). They are alike in that they both attempt to offer natural explanations (the tools of the sciences, such as logic, are part of or come from philosophy). But they are different in scope. Philosophy deals with the broadest abstractions, things which apply universally. Philosophy differs also from physical science in particular because it does not involve quantitative measurement or mathematics, which is distinct to physical sciences.

The attempt to replace metaphysics (a fundamental branch of philosophy) with physics is an error because any interpretation of physics necessarily assumes and depends on some form of metaphysics. Conclusions about the identity and nature of particular entities relies assumptions about the nature of reality and what it means to have an identity. To attempt to discard metaphysics is to still have a metaphysics, merely an unexamined one.

Likewise the scientific method cannot replace epistemology (the other fundamental branch of philosophy) because it is through epistemology that we form a philosophy of science, and through philosophy of science that we form a scientific method. You end up with the root again, this time epistemology, assuming it without examining or validating it.

Naturally accepting or depending on a set of ideas without checking to make sure they are accurate leaves you unprotected from errors which can poison every conclusion which assumes them. If the philosophy you unknowingly assume is wrong everything else will be wrong.

Committing the same error, attempts to derive morality from biology do nothing more than interpret amoral animal behavior through the lens of the observer's own pre-existing and unexamined moral principles. The misguided biologists project their own morality onto “nature” and go on to claim that we should act by these principles merely because other animals (allegedly) act by them and they are “natural” (which would be an error even if animals really did have a morality).  

Having a belief system is inescapable as long as you are living and thinking. If you don’t draw conclusions consciously your subconscious will do it for you. There is no possible substitute.
You can know what you believe and why by consciously attempting to be consistent and accurate. Or you can absorb (often unconsciously and unknowingly) whatever beliefs you happen to encounter, without criticism.  

Confusing Philosophical Skepticism (a particular school of thought within philosophy) with philosophy as such is another common error. Philosophical Skepticism (not to be confused with skepticism in the normal sense) poses as a healthy and rational "Question everything." But in reality it is a nonsensical "Conclude nothing and believe nothing."

Of course, it fails to live up to either, since the philosophical skeptic believes that you should believe nothing and refuses to consider that knowledge could be possible, which is to say refuses to question Philosophical Skepticism.
Philosophy does not mean asking questions without ever accepting answers. Philosophy does not mean chronic uncertainty. This is only one (particularly bad) approach to philosophy. There are many other schools of thought.

The root of the word philosophy is well known to be the Greek philo “loving” and sophia “knowledge (or wisdom).” Failing to understand that the linguistic origin of the word is not the literal meaning or definition leads to all kinds of misconceptions. There are those who justify calling nearly anything “philosophy” because they can offer a loose connection to their concept of “wisdom.”
Extending the practice of treating word origin as meaning quickly illustrates the absurdity of the practice. The word
tragedy comes from the Greek tragos “goat” and oide “song.” Obviously “goat song” is not a valid definition of tragedy. And word origin is not a valid standard of definitions.

The actual valid definition of Philosophy, as you can probably see emerging from the discussion of the concept, is the study of the basic nature of existence and our relationship to it.

This discussion has not given you a perfect understanding of philosophy. Hopefully it has given you a general idea of what philosophy is, a more valid concept. Really understanding it comes from the details. Navigating through the different branches, sub-branches, and key concepts can give an in depth understanding of the subject. And looking at the implications and applications of these parts will show their significance and that of the whole.