When an XML Element is defined inside another elements it is said to be nested inside another element and this process is known as “XML Element Nesting”. All the nested elements are child of the container tag (Parent Tag).
<subject>Test Message 1</subject>
In the above example “from”,”subject” and “body” tags are nested inside the “message” tag which is itself nested inside root element “inbox”.
It is necessary to have all XML elements must be properly nested within each other and child element should be closed before parent element in specified order.