An admission may be made orally or contained within a writing.
[3] Where the admission is in the form of a written record or document, and evidence is offered to prove the contents of the written record, the best evidence rule applies to require that an original document must be used in evidence unless it is unavailable.
This rule, however, only applies when evidence is offered to prove its contents.
In the United States, "Admission by a party-opponent" is explicitly excepted from hearsay under the Federal Rules of Evidence.
Among several types of admissions, the rule notes that an admission can be the "party's own statement" or a statement in which the "party has manifested an adoption or belief in its truth.