Verification is a declaration swearing that statements made in a document are true. Depending on the jurisdiction, verifications are either made under oath or in the presence of a notary public or similarly authorized person. Verifications are traditionally attached to the end of all pleadings that are required to be sworn. Also called affidavit of verification.
See, e.g. Business Guides, Inc. v. Chromatic Commc'ns Enterprises, Inc., 498 U.S. 533 (1991).