Disambiguations (Desambiguaciones, en Inglés)

Agnosticism refers to the impossibility of knowing/proving there's or there's not a "being outside time and space that created the universe" that's an unfalsifiable, therefore I am Agnostic.

Atheism refers to the BELIEF, that is, the way you conduct your life everyday based upon previously acquired knowledge. You know the Earth orbits the Sun, so you know why the Sun is going to rise on the East the next day. You get up in the morning without having to think about orbits everyday, therefore you BELIEVE the Sun is going to rise tomorrow. I don't have proof to believe god exists or not, but the evidence shows god is a unnecesary shenanigan to explain life the universe, and everything else. If you don't agree with that, you either haven't looked properly at the evidence, or you are in denial. Simple as that. Since I know god is unlikely, I therefore lead my life as if there's no god, therefore I am Agnostic Atheist.

Anti-Theism refers to the political dimension of religions, criticizing how it contributes magical thinking, submission to clergy, fanaticism and superstition. It also refers to the moral ground, stating that a god that, according to the bible, commands ethnic cleansing, infanticide (abraham), slavery and stoning of women (among other things) is LESS moral than any human been alive today, therefore I am: Agnostic Atheist AND Anti-theist.

So it's 3 different dimensions: Knowledge, Belief and Politics. Sometimes, 'Atheism' is just the shorthand word for all three, sometimes just the first two.