Google Earth

3D Geometry
This includes geometric representations of people, places and things.
Animation
Client opt-in time sequenced movement of 3D models and POIs eg. Santa Tracker Earthskin - the lights blink on and off
EarthskinTM
An organized collection of information that is located geographically on 3D interfaces such as Google Earth. The information within an Earthskin may entail some if not all of the following: 3D Geometry, Orthorectified Digital Aerial Photography, Overlay, Point of Interest (POI) or Balloons, Polygons, Animation.
KML
Keyhole Markup Language (KML) is an XML-based language for managing the display of 3D geospatial data in Google Maps and Google Earth. All programming on these 2 platforms are done in Keyhole Markup language. Here is the official documentation for KML http://code.google.com/apis/kml/documentation/
Further reading: http://en.wikipedia.org/wiki/Keyhole_Markup_Language
KMZ
The compressed version of the KML with the extension .KMZ
Network Link
A network link is associated with dynamic content. Each time a KMZ is loaded, the network link downloads new content if available. Network links are also used to distribute real-time data such as sports scores and weather updates.
Different states of a Network link:
Online - This means you have the most updated content
Offline - Refresh this icon if the network link is in this state
Orthorectified Digital Aerial Photography (Orthopics)
Orthopics are images that have any distortion caused by optics and shooting angles corrected making them suitable for tiling in applications such as Google Earth.
Overlay
Jpeg or png images of the following: High - satellite, Medium - low flying aerial photography, Ground - jpegs and pngs, Legend - Stationary jpeg and png that is stationed at one point.
Point of Interest (POI) or Balloons
Hyperlinks - links to web pages
Video - either hyperlinked to other web pages or embedded within the POI (embedded can only be viewed with Google Earth 4.2.0180.1334 (beta))
See also Waypoints and Popups
Polygons
A geometric area or shape defined by three or more points. Multiple polygons used together can define volumes used to represent people, architecture or any other 3D object.
Popups or Balloons
See also POI and Waypoints
Further Reading: http://www.geosmack.com/help/tutorials/
Waypoints
Predetermined geographical positions on 3D browsers used for virtual exploration and tours.
See POI
Definitions