Agnosticism
One who doesn't know if god(s) exist. This includes strong agnostics, those who don't believe it's possible to know if god(s) exist, agnostic theists, those who believe in god(s), but aren't sure if they exist, and agnostic atheists (sometimes called weak atheists), those who lack belief in the existence of god(s) (note: excludes strong atheists, those who assert the non-existence of god(s)).
Person A: I'm an agnostic. I don't know if there are any gods, so I'm making no claims about their existence.
Person B: I'm an atheist and I hold this same view, as Person A's agnosticism doesn't assert the existence of any gods. In this case my atheism is the same as Person A's agnosticism, though if I was a strong atheist I would still be an atheist,  but not an agnostic.
Person C: I'm an agnostic theist and I assert that a god exists, though I'm not entirely sure. My agnosticism is different from Person A's an Person B's as I assert the existence of at least one god.
Person D: I believe it's impossible to know if any gods exist, thus I am either theistic or atheistic in my views on the existence of god as a theist could believe it to be impossible to know if god(s) exist, just as an atheist could assert it's impossible to know if god(s) exist.