Preamble
A preamble is an introduction to a document that describes the documents purpose. The word comes from "pre" meaning "before" and "amble" meaning walk. A preamble can contain facts about the document. The preamble of a law is not part of the law but explains its purpose. The preamble of a book is called a preface. The preamble of a musical composition is a prelude or overture. The preamble of a Wikipedia article walks before the sections, and is called the lede or introduction.