Is locking up people who post child porn illegal?

I've heard that 1) it's illegal to make child porn, which I agree with it. But then I've heard that 2) it's *also* illegal to have it on your computer even if you didn't make it. How does that work? If someone in person asks you if you want some child porn, it's obviously illegal. But if someone posts it online, *everyone* can see it. How does that not violate 1?<br><br>A further question: is it illegal to use AI to make child porn? If so, why?