XML documents form a tree structure that starts at

the root

An

XML tree

starts at a

root element

and branches from the root to

child elements

<root>
  <child>
    <subchild>.....</subchild>
  </child>
</root>

The terms

parent

,

child

, and

sibling

are used to describe the relationships between elements. ...

Parents

have children.

Children

have parents.

Siblings

are children on the same level (brothers and sisters). ... We can use any of the online XML tree viewer tools to see the document's tree structure, like this one:

https://www.xmlviewer.org/

Books

XML document to see on tree-viewer

<books>
  <book category="cooking">
    <title lang="en">The goals</title>
    <author>Giada De Laurentiis</author>
    <year>2007</year>
    <price>30.00</price>
  </book>
  <book category="children">
    <title lang="en">12 rules for life</title>
    <author>J K. Rowling</author>
    <year>2002</year>
    <price>29.99</price>
  </book>
  <book category="web">
    <title lang="en">The richest man in Babilon</title>
    <author>Erik T. Ray</author>
    <year>2001</year>
    <price>39.95</price>
  </book>
</books>