What is atheism exactly, and why are they against people believe in a God or gods? Why can't we all just believe what we want?

You can absolutely believe anything you want at all.
You cannot require others follow your beliefs by enforcing it with law nor can you expect that having a belief will make said belief immune from questioning.

Atheism, to be exact, is a lack of belief in any deities.

They are not by definition against people that believe in god(s), that would be anti-theists, which is different.

I'm personally not against people who understand that religion does not belong in government/public schools and who do not become violent over their religion believing whatever they want

You can believe whatever you want, just don't use tax dollars to inflict your views on everyone else.

Theism is the certainty
that at least one imagined deity
is actually real.

Atheism is the lack of that
single defining certainty.

Believe whatever seems true to you.
Just don't try to legislate your beliefs
onto me.

--
Regards,

John Popelish

Atheism is a lack of belief in gods...

You can worship a holy fire hydrant if you want to as long as you keep it to yourself and do no harm because of it...

IMHO

The atheists I know in my personal life are fine with my beliefs. Many of the atheists and antitheists on this site are too narrow minded to accept that not everyone can agree.

The only defining characteristic of atheism is a personal lack of belief in god. Instead of asking a really stupid question and giving me an extra 2 points, educate yourself.

There's just enough religion in the world to make men hate one another, but not enough to make them love.

I'm an atheist, i was religious once.
Atheism is the lack of a belief due to the lack of evidence. Religious apologist often say we can't see beyond what we know, i fully agree with that but i am not too open minded to just accept any unfounded claims without first examining the information i was provided. If science cannot explain it that does not mean religion can. To assume god did it is to commit a fallacy known as, "the god of the gaps fallacy."

I am against religion because, not only that it cannot prove itself and it's ultimate claim that God exists, it expects people to treat it as if it is a real thing. You are taking real life actions that Are based on a foundation that can be questioned. That is why you have people who does all kinds of ridiculous and morally unacceptable things, in a modern perspective.

Also, religious people often actively deny scientific facts and theories. We are all entitled to our own opinions yes? True but when something becomes a proven FACT, it is no longer up for opinions anymore and is not controvertible unless you can provide testsble information to support your claims. Otherwise, to deny facts is as ridiculous as saying the "earth is flat." Such misinformation and ignorance is not preferable to a modern civilisation and is not a respect to the human intellect.

1.) Read the dictionary on what atheism is; stop being lazy
2.) Because they want to influence laws and make exceptions for their religion.
3.) Terrible idea to not be critical of beliefs. Belief is the acceptance of ideas/concepts without evidence, totally irrational. Beliefs can warp people's thinking to do things they wouldn't otherwise do, usually resulting in pain and violence.

People with your beliefs kill for their beliefs so there is no place in the modern world for your kind.

Pay attention:

atheist = no belief in any god(s)
atheist =/= anything else

Most of us don't particularly care what others believe. We only get annoyed when believers try to force their beliefs into everybody else's life.

History became part of our lives.. G-d is the way to believe in after G-d decided to make people believe in. After G-d decided to do it, some people remain too skeptical. You are free if you live in the USA or such places like even Muslim or Arab countries, but you still go to hell Probably. If you are in Israel, the G-d's law says you must be killed for denying truth of history.

Thanks!