Many uneducated twits appear on this site, declaring themselves to be "Atheists" or "agnostics".
Some, even less educated, call themselves "Athiests".
Usually, these people don't know what "atheist" and "agnostic" mean. They don't even know that as neither is a concrete philosophy, neither is a proper noun and thus
should not be capitalized.
Internally, we True Christians™ know that an "atheist" is someone who loves sin and hates God so much that he pretends God doesn't exist. Some even convince themselves!
But there are some particular "accepted" definitions, which most of our visitors still don't seem to grasp. A link to confirm, from a noted God-hating atheist site, is
HERE.
I'll simplify a bit.
A "gnostic" is someone who believes we can/do know God.
An "agnostic" is the opposite; someone who believes it is not possible to/we do not know God.
A "theist" actively believes in a god or gods.
An "atheist" does not actively believe in a god or gods.
Note that, unlike the typical thought process of the uneducated atheist, there is no continuum of "theist" <--> "agnostic" <--> "atheist".
There is "gnostic" <--> "agnostic" and there is "theist" <--> "atheist".
No overlap. They are not related words.
That is how we have "gnostic theists", like True Christians™, who know that we can know God and who believe in God.
We also have "agnostic theists", who don't think we know or can know God, but think that some sort of god-type thing is probably floating around somewhere. Most self-described agnostics are actually agnostic theists.
Then there are "agnostic atheists", which is what most self-described atheists are. They say, "I don't think there's a god or gods because I haven't seen any evidence, and I don't think there's evidence that we can understand." The agnostic atheist is still open to evidence, and recognizes that saying "I know there is no God", since it is not possible to prove a negative, is an act of faith instead of knowledge. For example, the "agnostic atheist" thought process would lead to a statement like, "I don't believe there are leprechauns because, even though I can't prove there are no leprechauns in the universe anywhere, I've never seen evidence adequate to persuade me to believe leprechauns exist."
Finally, the true God-haters are "gnostic atheists". They are certain that we would know God if He were out there, and therefore are certain that He is not out there. They are every bit as faith-driven as True Christians™; we understand their true motive to be a desire to live a life of sin, so they choose to believe there is no God to punish them for their perversions.
"Antitheists" are a whole separate bunch. These are people who are against religion in all its forms, because they think it is destructive to humanity.
I hope this has been educational for you.