People of faith will always have a hard time understanding why a fellow human being would choose to be either Atheist or Agnostic. That's OK. But there are vast differences between the beliefs and attitudes one can expect from either camp, and it's not accurate or fair to lump them together, though it is tempting.
What follows is a guide to understanding the difference between these two loaded A-words.
Atheists have firm beliefs. They are not wishy-washy about the subject. An Atheist quite simply believes there is no supreme being. Adherents espouse no religious beliefs whatsoever, and the majority has no desire to "convert" believers. Those that do are often called "militant atheists", but they are few in number.
Agnostics don't assume. The very word "Agnostic" means "without knowledge." In essence, an Agnostic most frequently believes that the divine is unknowable. This position indicates an absence of faith, certainly, but that runs both ways. An Agnostic does not have certainty that there is a god, but he would never state absolutely that there is not a god, either.
Strong or Weak? As with anything practiced by human beings, there is division within the ranks. A strong Atheist might state flat out that no god exists and that nothing will sway him from his position. A so-called weak Atheist will deny the existence of god based on a lack of evidence. Following that logic, one could say that presentation of new evidence might sway the weak but not the strong. Among Agnostics, the "weak" position allows for the faith of others, in essence stating that faith is a reasonable form of belief, but not for this fella. A "strong" agnostic believes categorically that no human being can reasonably claim to know that a supreme being exists.
Religion or Philosophy? Some might argue that Atheism and Agnosticism shouldn't even be included in the consideration of religions. There is some merit to that thought. While the world's religions attempt to sort out how to best serve the divine will, Atheists and Agnostics declare it to be none of their concern. Agnostics often claim that they do not concern themselves with belief at all, but only with knowledge.
Famous Names. Well-known proponents of Atheism include: Ambrose Bierce, Karl Marx, Friedrich Nietzsche, Robert Frost, Jean-Paul Sartre, and John Lennon. Agnosticism was claimed by Charles Darwin, David Hume, Clarence Darrow, H.L. Mencken, and Bertrand Russell. Writer and academician C.S. Lewis was famously an Atheist who converted to Christianity and turned his formidable intellect to the issue of faith from that seemingly paradoxical perspective.
Whither morality? Some Atheists and Agnostics believe that ethics and morals are relative to each individual, but most believe that their morality has a stronger base than that of a theist, because it does not require an outside arbiter to uphold it. They will also point to wars and atrocities committed in the name of religion as proof that faith does not dictate morality. Still others would say that morality is a separate issue from their stance on religious belief.
Most of us are raised with one kind of faith or another. For those who question the value of devotion to the unseen, many options exist. One can work within his chosen theology to find an acceptable answer, or seek out other belief systems that may appeal more to him. He can refuse to believe or else come to terms with the concept that the machinations of the divine are beyond his ken. By using this guide, hopefully any curious soul will at least be able to grasp the differences between these two approaches to the fundamental question.