An appeal is a challenge to a previous legal determination. An appeal is directed towards a legal power higher than the power making the challenged determination. In most states and the federal system, trial court determinations can be appealed in an appellate court. The rulings of those appellate courts may be reviewed by a "court of last resort." In the federal court system, that is the United States Supreme Court.
The person pursuing an appeal is called an appellant, while the person defending the lower court’s ruling is the appellee or respondent.
Appeals can be either discretionary or of right. An appeal of right is one that the higher court must hear, if the losing party demands it, while a discretionary appeal is one that the higher court may, but does not have to, consider. For example, in the federal system, there is an appeal of right from the District Court to the Court of Appeals but appeals from the Court of Appeals to the Supreme Court are discretionary.
Appeals do not always originate from court decisions. In administrative law, people are often allowed to appeal, in court, the decisions made by executive agencies.
See also: Appellate Jurisdiction and Appellate Procedure[Last updated in June of 2022 by the Wex Definitions Team]