I'm agnostic for a number of reasons, allow me to explain some of them so that you understand why there is such a thing as agnosticism.
Christians believe in a giant santa claus in the sky, he's a benevolent god who kills them when they prey for medical cures (sorry, that's the scientific fact, you are less likely to survive an illness if you are aware of someone praying for you, seriously), he needs money and has a collection bowl like a vagabond, but is all powerful and all seeing.
Atheists believe that there is no God. Typically enforcing their beliefs with acceptance of various widely accepted 'probable' scientific theories.
I do not believe in the Christian, or any other, God. These are clearly bunk on the face of the evidence available and no rational person would believe in them. In this much I can agree with the atheist argument.
But I do not know if there is actually A God. Clearly not Yahweh/Jehova as the factual evidence of the bible you can only believe with double speak in denying the history behind the birth of the bible. But some other thing that Humans have not written a story for? Maybe.
However, I consider another question more important. Whilst the theists would suggest the most important is "Is there a God?", to me this question is really a moot point.
I ask instead, "Does it matter if there is a God?".
See I don't care about how the universe came into being, I really don't give a damn. I already know it came into being I really don't care how. I don't understand why answering that question is so important.
So I really don't give a damn if there is a God or not.
I'll tell you this much though - no Human ever had enough information available to make an educated assumption about why we are here, let alone know the truth, and no God ever spoke to a Human. To me, belief in theism or atheism is a pretty arrogant stand point as it elevates the importance of the Human race. Whilst we may well be capable of collapsing waveforms, we're not the centre of the universe, and the universe will carry on just fine after we're gone.