About KML Files
What is KML?
Keyhole Markup Language (KML) is an XML-based language schema for visualizing geographic annotation on two-dimensional maps and three-dimensional Earth browsers.
The KML file specifies a set of features (placemarks, images, 3D models, textual descriptions, etc.) for display in a KML application. The most common of these is Google Earth, but there are a number of other 3D earth browsers and viewers which implement the KML encoding.
Each place located by the KML file uses a minimum of a longitude and a latitude. If additional data is provided, the view can be more specific - for example a "camera view" uses further details such as such as tilt, heading and altitude. Enriched KML files are often distributed as KMZ files, which are zipped KML files with a .kmz extension. When a KMZ file is unzipped, a single "doc.kml" is found along with any overlay and icon images referenced in the KML.
You need a KML viewer
The
first step to using any KML file is to have an application
or browser plug-in which is capable of handling this file
format. We'll use Google
Earth as the example here.
How to use a KML file

When you click on link to get a KML file for the first time, your browser may not know how to handle this file format, and will simply offer you the opportunity to download it. This means you'd then need to locate the .KML file on the computer's desktop (or wherever you have set the default download folder to be) and double click on that file to launch Google Earth.

Need More Help with Google Earth? |
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Excellent Google Earth Help files and documentation are available. |
Google Earth User Guide |