Atheism is a belief; it establishes a single absolute conclusion to the same question.
Agnosticism is not a belief; There is no conclusion drawn because of a lack of supporting evidence. When god can be proven or dis-proven mathematically or personally then a decision will be made.
Other religions are beliefs; drawing absolute conclusions without verifiable explanations.
The difference between atheism and agnosticism is artificial and of recent origin.
Most people who are not religious now, are not religious for the same reason: There is no proof that a god is required for the universe to exist.
Any reasoning person, when shown incontrovertible evidence of something, must come to accept that same something. It's how science works.
Show me simple, repeatable and verifiable proof that god exists, and I'll be a believer.
I wouldn't consider the difference between Atheism and Agnosticism artificial.
It's the difference between "I don't believe in God" and "I don't know if God exists, or in what manner or form God may or may not exist."
I view it as the difference between choosing an answer and searching for an answer... This isn't a time sensitive question where the lack of an answer counts as a "no."
Or, it's the difference between "I don't believe in God because I've seen no evidence a god exists" or "I don't know if God exists, or in what manner or form God may or may not exist because I've seen no evidence a god exists".
It's no good trying to define a way of thinking without defining its basis. Saying "Atheists don't believe in god" without referring to why they don't believe in god provides no insight into what atheism really is.
In the example I gave above atheism == agnosticism. You'll be able to give an example where atheism != agnosticism. This is why I call the distinction artificial, since adding a reason for the statement changes the meaning of the statement.
I feel like this is one of those awkward debates where both of us actually agree on the topic at hand, yet we both use clever wording which forms a distinction between our points that allows the debate to actually continue...
I'll continue our little agreement/debate:
"I don't believe in God because I've seen no evidence a god exists" is along the same lines as making the assumption that X + 40 = 42. Unless you know the value of X you shouldn't consider your answer to be correct.
"I don't know if God exists, or in what manner or form God may or may not exist because I've seen no evidence a god exists" is comparable to saying X + 40 = Y. You don't know the answer so you leave it as a variable.
(X + 40 = 42) != (X + 40 = Y)
Atheism is a belief based on a lack of evidence and parallels religious belief.