KML or Keyhole Markup Language is a file format used to render geographic data in an Earth browser such as Google Earth. KML is a global standard maintained by the Open Geospatial Consortium. It uses a tag-based structure with nested elements and attributes. KML is based on the XML standard, and all tags are case-sensitive and must appear exactly as they are listed in the KML Reference. The Reference shows which all tags are optional, and within a given element, tags must appear in the order shown in the Reference. KML files can be created to pinpoint locations, expose rich data in new ways and add image overlays.