An individual may choose to file for an appeal at the conclusion of his criminal trial. An appeal asks a court of a higher jurisdiction to look at the presented issues and decide if the lower court made a mistake. An appeal is not a new trial nor is it a way for the defendant to present a new defense.
An appellate court will not determine the facts of a case. In addition, no witnesses or new evidence can be presented. The court will only read the transcripts and appellate briefs that are filed by the defendant and prosecutors.
During the appeal, a judge may decide to grant the defendant with bond while the appeal is being decided. In most cases, the judge will not grant a bond because the defendant was already found guilty and sentenced.