Each XML document must have one—and only one—document element, which is sometimes referred to as the root element.
Be careful if you use or read the term root without any further clarification. The XML 1.0 specification uses the term apparently as a synonym for the document entity (Chapter 2 of the XML 1.0 Recommendation) and also as a synonym for the document element (Chapter 2.1).
Typically, nested within the document element is a hierarchy of other elements, represented as start tag/end tag pairs or as empty element tags.
Elements must be nested correctly. The following ...