Atheism is just one non-religious world-view philosophy (not a religion or belief system, atheism is a philosophy). As non-religious groups are so misunderstood by theists (a person who sees the world in a supernatural world view). I have outlined the other non-religious world-views as well as atheism.

Humanism: "a non-religious philosophy based on liberal human values" (The Australian Oxford Paperback Dictonary, secound edition)

"The beginning of wisdom is the awareness that there is insufficient evidence that a god or gods have created us and the recognition that we are responsible in part for our own destiny. Human beings can achieve this good life, but it is by the cultivation of the virtues of intelligence and courage, not faith and obedience, that we will most likely be able to do so." Paul Kurtz

"I feel no need for any other faith than my faith in the kindness of human beings. I am so absorbed in the wonder of earth and the life upon it that I cannot think of heaven and angels."
Pearl S. Buck

Agnostic: " A person who believes that nothing can be known about the existance of God exept material things" ( The Australian Oxford Paperback Dictonary, secound edition)

"I do not consider it an insult, but rather a compliment to be called an agnostic. I do not pretend to know where many ignorant men are sure -- that is all that agnosticism means"- Clarence Darrow

I don't spend much time thinking about whether God exists. I don't consider that a relevant question. It's unanswerable and irrelevant to my life, so I put it in the category of things I can't worry about.-Wendy Kaminer

Agnosticism is oftern greatly misunderstood as it when a person neither believes there is a god or there is not a god.  It is sometimes thought to be in the middle of theism and atheism. Neither a theist or atheist.

Atheist: "A person who believes that there is no god" (The Australian Oxford Dictonary, secound edition)

"A man's ethical behavior should be based effectually on sympathy, education, and social ties and needs; no religious basis is necessary. Man would indeed be in a poor way if he had to be restrained by fear of punishment and hope of reward after death".  Albert Einstein

Atheism is the acceptance that there is no credible scientific or factually reliable evidence for the existence of a god, gods or the supernatural.

As atheism is so misunderstood atheist's are oftern in the awkward possition of theists defining their beliefs and their ethical perspective as they do not understand it. The label that thiest put on atheist's is "EVIL" and "Worshiper of Satan" (but since atheist's don't believe in any supernatural beings- including Satan how could we worship Satan)

To defin atheism, there are 3 types of atheism:

Implicit athesm- This is when a person does not consiously reject god/gods. They are not taught about religion or understand it.

Emosional atheism- when a person consiously rejects god/gods to rebel against society without evaluation of it.

The rejection of all gods by objective evaluation and sees the world through a naturalistic world view apposed to the supernatural world view of theists. They face reality as it really is and in a possitive and constructive way.

Atheism is only about the non-existance of all gods nothing else. It does not set out ethics, morals and values. It is not necessarily an anti-religious possition. Each atheist sets out their own morals and values from what they see are being morally correct. Religious people's morals are set out by their gods/texts. Religious people are moral because they are scared they will be punnished by their gods or suffer in the afterlife. Atheists just set their own morals from their education and upbringing. Religion is not needed for morals, religious people seem to think so though.

Atheists can be in fact be happier people as they do not waste their time on artifical gods. They don't confirm to society's way of thinking. They are free thinkers- they have open minds and dont accept or are gulable and accept what most people just willingly accept depending purely (usually) on what country your from.  They believe that they need to work to achieve in everything including the world and themselves. If they want something to happern they do not pray for it they get out there and do it they dont wish for it as there is no 'cloud guy' that is going to possibly do it.

What atheism isn't:

-Being angry at God- this is apostasy

Modern Atheism's history:

Modern Atheism is a post-Enlightment, European phenomenon. The Enlightment waa an 18th centrry European movment of philosophy and science stressing reason over ancestral tradition and supernatural belief.

Advances in science and knowledge of the natural world enabled Charles Darwin in the secound half of the 19th century to outline his theory of evolution.  Science challenged religious understanding of creation.

Most atheists have analysed the avaliable material evidence of one or more gods/goddesses and have concluded that there is no real evidence for the existance of any supernatural beings.