Google Earth is a program for viewing the globe of the earth in a semi 3D fashion. In addition one can search for place names or landmarks. It is also possible to hook up GPS decvices since the Google Earth Pro version is free nowadays.
The geographical information is pulled from a Google server. A broadband internet connection is therefore de-facto a requirement. Google Earth basically shares the same data as Google Maps. Google Earth however features a richer functionality including 3D navigation around the globe.
We created a sample page with a 3D representation of downtown Delft. If you want to create your own 3D model then you software to convert data into the KLM format. This is possible with the (free) Open 3D Converter software in the Downloads section. The software is free to download and use. Sample data can be downloaded in this section as well.
For more information refer to the Google website: http://earth.google.com.