Namespaces in an XML Document
XML namespaces associate element and attribute names in an XML document with custom and predefined URIs. The prefixes defined for namespace URIs are used to qualify element and attribute names in XML data to implement this association. Namespaces prevent element and attribute name collisions, and allows elements and attributes of the same name to be handled differently and validated differently.
For more information on how to select namespace-specific XML data from an XmlDocument, see the XmlNameSpace Sample.