Agnosticism is basically saying that you can neither confirm or deny the existence of any deity.
Atheism is denying that there is any deity in existence.
I see what you mean though.
No, you're completely wrong (though I don't blame you, people use "agnostic" incorrectly all the time). "Gnostic" and "Agnostic" refer only to knowledge, any sort of knowledge. "Gnostic" is "knowing", "Agnostic" is "unable to know". See here for a more in-depth explanation.