Appellate review refers to the power of a higher court to examine the decision or order of a lower court for errors. Appellate procedure consists of the rules and practices by which appellate courts review trial court judgments. Appellate review performs several functions, including: the correction of errors committed by the trial court, development of the law and precedent to be followed and anticipated in future disputes, and the pursuit of justice. In reviewing errors of the lower court, the errors focused on are of a legal nature, appellate courts will usually not disturb factual findings.
Several issues are foremost in appeals, such as what judgments are appealable, how appeals are brought before the court, what will be required for a reversal of the lower court (e.g., a showing of "abuse of discretion," "clear error," etc.), and what procedures parties must follow.
In order to bring an appeal, there must be a finality in the decision or order appealed. See, for example, the federal "final judgment rule" at 28 U.S.C. § 1291. There are, however, exceptions to the "final judgment rule." They include: instances of plain or fundamental error by the trial court, questions of subject-matter jurisdiction of the trial court, or constitutional questions. See, for example, the Federal statute on appealable interlocutory (non-final) decisions at 28 U.S.C. § 1292.
Arguments upon appeal are made mainly through written briefs, which present the questions on appeal and cite the legal authorities and arguments in support of each party's position. A minority of jurisdictions allow for oral argument as a matter of course. Where allowed, oral argument is intended to clarify legal issues presented in the briefs. Ordinarily, oral arguments are subjected to a time limit extended only upon the discretion of the court. De novo review is an appeal of a lower case which grants a new trial, so that the case is heard as if for the first time and facts as well as law are examined.
There are dual systems of applicable to appeals. Federal appellate courts are governed by the Federal Rules of Appellate Procedure. State appellate courts are governed by their own state rules of appellate procedure.