A Keyhole Markup Language file is one with a .kml extension. By holding locations, picture overlays, video connections, and modeling information such as lines, forms, 3D images, and points, KML files use XML to convey geographic annotation and visualization. KML files are used by various geospatial software tools to convert data into a format that other programs and web services can understand. Before Google acquired Keyhole, Inc. in 2004 and began using the format with Google Earth, this featured Keyhole Earth Viewer from Keyhole, Inc. http://kmlconverter.com/blog/what-is-kml-file-and-how-do-i-open-it
