A KML file is a keyhole markup language file and is one of the GIS (Geographic Information System) file formats. KML, like HTML, is a markup language and includes geographic information in vector form, such as points, lines, and polygons, as well as in raster form, such as aerial or satellite images. All data is stored with an XML syntax.
The KML format was originally developed by the satellite image company Keyhole Corp. Developed, but this was taken over in 2004 by Google. KML has been recognized as the standard by the Open Geospatial Consortium and is the file format for Google Earth and Google Maps.
Google Earth processes KML files in much the same way as a browser processes html files. In addition to the file extension KML, the extension kmz is also used for compressed KML files. These are just a ZIP archive that contains the embedded data, such as textures and 3D models as separate files.
Some programs require the King.KML FDO Provider for KML or a special script to import the files. Newer versions often support the format natively.