XML Schema is an XML-based replacement for DTDs.

XML Schema describes the structure of an XML document.

The XML Schema language can also be referenced as XSD (XML Schema Definition).

XSD - <schema> element syntax

The

<schema> element is the root element of every XML Schema.

XSD - <schema> element example

<?xml version="1.0"?>
<xs:schema>
...
...
</xs:schema>