KML (Keyhole Markup Language) is an XML-based schema for managing 3D geospatial data in the program Google Earth (previously called Keyhole before it was bought up by Google). KML files are often distributed as KMZ, zipped KML files. The KML file specifies a placemark for Google Earth. It contains a basic description of the place, longitude, latitude, tilt and some other information. KML files serve a similar purpose as worldwind:// urls in NASA World Wind but contains more information than just the longitude and latitude.
Example KML document
<?xml version="1.0" encoding="UTF-8"?>
<kml xmlns="http://earth.google.com/kml/2.0">
<Placemark>
<description>New York City</description>
<name>New York City</name>
<LookAt id="khLookAt539">
<longitude>-74.0063934326172</longitude>
<latitude>40.71417236328126</latitude>
<range>618.7009686335238</range>
<tilt>-4.812906559956015e-026</tilt>
<heading>-1.937595207549944e-014</heading>
</LookAt>
<Point>
<coordinates>-74.0063934326172,40.71417236328126,0</coordinates>
</Point>
</Placemark>
</kml>