So little one, in the United States, there are rules and laws about what people can see and hear in public. Some things like swearing or showing private parts of the body are not allowed because they are considered bad for children or offensive to some people.
One kind of bad thing that is not allowed by the law is called obscenity. This means things that are really really sexual and nasty in a way that people usually don't talk about in public. Like talking about sex in a way that makes people uncomfortable, or showing pictures or videos that are gross and dirty.
The way they decide if something is obscene or not is by using something called the "Miller Test." This test says that something is considered obscene if it either:
1. Doesn't have much purpose other than making people feel sexually aroused,
2. Shows sexual acts that are really shocking, beyond what people normally do, and
3. Is sexual in a way that doesn't have any real artistic, literary, or scientific value.
So, if somebody makes something really dirty or gross like that, they can get in trouble with the law. But if something has a real purpose or value, it might be okay even if it includes sexual stuff.
That's why it's important to always use good judgement and choose things that are appropriate for different settings and ages.