A more thorough explanation:

An appeal brief is a written document prepared by a party's lawyer to present legal arguments and facts to a higher court, usually in an appellate case. It is a formal way of arguing why the lower court's decision was wrong and why the higher court should reverse it. The appeal brief contains legal and factual arguments, as well as references to legal authorities that support the party's position.

For example, in a patent case, a patent applicant may file an appeal brief to the Board of Patent Appeals and Interferences, arguing that the patent examiner was incorrect in rejecting the application. In a criminal case, the defendant's lawyer may file an appeal brief to argue that the lower court made a mistake in convicting the defendant.

The appeal brief is an important tool for parties to present their case to the higher court and persuade the judges to rule in their favor. It is a formal and structured document that follows specific rules and guidelines, such as the length of the brief, the font size, and the citation format. The appeal brief is usually accompanied by other documents, such as a record of the lower court proceedings and a reply brief that responds to the arguments made by the other party.