Rules of evidence are, as the name indicates, the rules by which a court determines what evidence is admissible at trial. In the U.S., federal courts follow the Federal Rules of Evidence, while state courts generally follow their own rules. In establishing what evidence is admissible, many rules of evidence concentrate first on the relevancy of offered evidence. Rules of evidence also allocate among the parties the burden of producing evidence and the burden of persuading the court. The Federal Rules of Evidence also address the admissibility of hearsay, and oral testimony.