A more thorough explanation:

The Interlocutory Appeals Act is a federal law that was passed in 1958. It allows a U.S. court of appeals to review an interlocutory order in a civil case if the trial judge states in writing that the order involves a controlling question of law on which there is substantial ground for difference of opinion, and that an immediate appeal from the order may materially advance the termination of the litigation.

For example, if a trial judge issues an order in a civil case that both parties disagree with, one party may ask the court of appeals to review the order under the Interlocutory Appeals Act. The court of appeals will only grant the request if the judge's order involves a question of law that is important to the case and needs to be resolved before the trial can continue.

The Interlocutory Appeals Act is different from the finality doctrine and final-judgment rule, which generally require a case to be fully resolved before an appeal can be made.