A more thorough explanation:

Public controversy refers to a disagreement or dispute that is debated publicly and has significant consequences for people other than those involved in the dispute. It can involve issues such as politics, social justice, or public policy.

For example, a public controversy could be a debate over whether a particular law should be passed or repealed. This type of controversy can involve many people and can have a significant impact on society as a whole.

Participants in a public controversy may be considered public figures, which means they are subject to greater scrutiny and criticism than private individuals. This is especially true if they are involved in the controversy voluntarily, have access to channels of communication to counter false statements, and play a prominent role in the controversy.

Separable controversy is a claim that is separate and independent from other claims being made in a lawsuit. This type of controversy is often associated with a statute that allows an entire case to be removed to federal court if one of the claims presents a federal question that falls under the jurisdiction of the federal courts.

Another type of controversy is an actual controversy, which is a case that requires a definitive determination of the law on the facts alleged for the adjudication of an actual dispute, and not merely a hypothetical, theoretical, or speculative legal issue. This type of controversy must be a real and substantial controversy that admits of specific relief through a conclusive decree, as distinguished from an opinion advising what the law would be upon a hypothetical state of facts.