location based services
KML, or Keyhole Markup Language, is an XML grammar and file format for modeling and storing geographic features such as points, lines, images, and polygons for display in Google Earth. This document describes version 2.0 for Google Earth version 3.0 and later. (Earlier versions of KML can be read into Google Earth and saved out as KML version 2.0.)
You can use KML 2.0 to:
Specify icons and labels to identify locations on the planet surface
Create different camera positions to define unique views for each of your features
Use image overlays attached to the ground or screen
Define styles to specify feature appearance
Write HTML descriptions of features—including hyperlinks and embedded images
Use folders for hierarchical grouping of features
Dynamically fetch and update KML files from remote or local network locations
Deliver current view details from the client to the server in order to fetch KML data based on changes in the 3D viewer
A KML file is processed by Google Earth in a similar way that HTML (and indeed, XML) files are processed by web browsers. Like HTML, KML has a tag-based structure with names and attributes used for specific display purposes. Thus, Google Earth acts as a browser of KML files.