KML 2.0 namespace
This is an XML namespace defined in the KML Language Reference specification for use with the Google Earth client.
For more information on KML, the markup language used to author content for Google Earth, please refer to the KML 2.0 specification. A tutorial is also available, and many examples of KML content are available at the Google Earth Community.
For more information about XML namespaces, please refer to the Namespaces in XML specification.