XML Schema is a language for describing the structure and constraints of an XML document. It provides a way to define the structure and data types for the elements and attributes in an XML document and can be used to validate an XML document to ensure that it conforms to the defined structure and constraints.
An XML Schema is itself an XML document, and it is used to define the structure and content of other XML documents. It can be used to specify the allowed elements, attributes, and data types for an XML document, as well as the relationships between these elements and attributes.
XML Schema provides a number of features that make it useful for defining the structure and constraints of XML documents, including support for data types, namespaces, and extensibility. It is widely used for defining the structure and constraints of XML documents in a variety of contexts, including in the context of Web services and other types of data exchange.