A more thorough explanation:

Obscenity refers to speech or artistic expressions that are not protected by the First Amendment. It includes lewd, filthy, or disgusting words or pictures. While indecent materials or depictions may be restricted in terms of time, place, and manner, they are still protected by the First Amendment. Each state has its own laws controlling obscene material.

The definition of obscenity has been difficult to establish, but the current standard is the Miller test. This test includes three criteria: (1) whether the work appeals to prurient interest, (2) whether it depicts sexual conduct in a patently offensive way, and (3) whether it lacks serious literary, artistic, political, or scientific value.

For example, a book that describes explicit sexual acts in a way that is offensive to the average person and lacks any literary or artistic value would be considered obscene and not protected by the First Amendment.

The Supreme Court has repeatedly grappled with problematic elements of the Miller test, but to date, no standard has replaced it. In 1997, the Court addressed obscenity in the field of new media with Reno v. American Civil Liberties Union (“ACLU I”). The case challenged the Communications Decency Act, which aimed to protect children by restricting transmissions sent over the Internet. The Court ruled that the Act was overly broad in its approach to regulating obscenity online.

Overall, obscenity laws are concerned with prohibiting speech or artistic expressions that are offensive and lack any redeeming value.