KML is an XML-based standard for geographic data, originally developed for Google Earth and Google Maps. It was recognized as an ISO standard in 2008, and KML has been maintained by the Open Geospatial Consortium ever since.
KML is often exchanged in KMZ zip packages. These zips usually contain associated files such as images.
Although KML is an open XML standard, application support is relatively limited. It should be possible to convert KML to the preferred GML format without losing data.
KML is a non-preferred format for file type GIS.