SketchUp is a 3D modeling program designed for professional architects, civil engineers, filmmakers, game developers, and related professions. It is also widely used by teens and pre-teens as an entertainment software. Most people however use it to design buildings to be displayed on Google Earth. It was designed to be more intuitive, flexible, and easier to use than other 3D modeling programs, which often have steep learning curves.[1] Several features allow designers to "play" with their designs, unlike what is possible in other 3D CAD programs. It is marketed as an easy-to-use conceptual tool with a simple interface. A well known feature in the SketchUp World is the 3D Warehouse. Users can use their Google Accounts to upload models, and then browse the 3D Warehouse for many components and models.
Some of its key features and uses include:

A "smart" drawing cursor (inference) system that allows users to draw 3D objects using a 2D screen and mouse.
Simple massing study capability via "push-pull".
An interactive Heliodon, or sun angle simulator.
Ability to animate camera and sun movements.
Models can be individually colored with an assortment of solid colors, textures and materials.
Interoperability with Google Earth.
Simplicity of use over other modeling programs for children, amateur artists, and hobbyists. History
Add-ons can be downloaded from the SketchUp Web Site's Plugins page.

Add-Ons
One such add-on allows the user to export the 3D model as a .kmz file which can then be opened in Google Earth. This allows accurate geo-referencing of SketchUp models and accurate placement of those models in Google Earth. It also allows SketchUp to import modeling context (photographic + terrain model) from Google Earth for modeling reference.

Google Earth
Other add-ons are provided for export to:

3D Text — for creating 3D text.
3ds Max
IRender — fully integrated Ray Trace Renderer for SketchUp using the AccuRender engine.
RPS 3D PDF for interactive 3D PDF documents.
RpReports — for assigning attributes and reporting on components..
RpTools — for wizard based manipulation of components. Other Add-ons

Tools

Drawing tools
This is used to draw a regular straight line.

Arc
This allows the user to scribble and create a freehand figure.

Freehand
The user can make circles by clicking a point and dragging out the radius.

Circle
Polygons are constructed in much the same way as circles; they are clicked and dragged.

Polygon
This tool is used to make rectangles with by clicking and dragging to adjust the length and width.

Rectangle

Editing tools
The push/pull is a tool that grabs a two-dimensional surface and pushes or pulls it into three dimensions. This, Google claims in the tutorial, is the main idea of Google SketchUp. U.S. patent #6,628,279 is a patent for this technology.

Push/pull
A protractor is used to angle selected geometrical pieces.

Rotate
The user's mouse can select and move pieces on the three different axes or on some combination of the three.

Move
Other useful tools can be found here

Link
SketchUp holds a Patent U.S. Patent 6,628,279  on its Push/Pull technology:
"System and method for three-dimensional modeling: A three-dimensional design and modeling environment allows users to draw the outlines, or perimeters, of objects in a two-dimensional manner, similar to pencil and paper, already familiar to them. The two-dimensional, planar faces created by a user can then be pushed and pulled by editing tools within the environment to easily and intuitively model three-dimensional volumes and geometries."
The patent was applied for in November 2000, and awarded in September 2003 (U.S. Patent 6,628,279 ).

Patents
On April 27, 2006, Google announced Google SketchUp, a freely-downloadable version of SketchUp.[6] The free version is not as capable as SketchUp Pro 6, but it includes integrated tools for uploading content to Google Earth and to the Google 3D Warehouse,[7] a repository of models created in SketchUp.
It can export 3D Google Earth .kmz files and 2D graphic: .bmp .png .jpg .tif. Google SketchUp Pro can export more 3D graphic files: .3ds .dwg .dxf .fbx .obj .xsi .wrl and more 2D graphic: .pdf .eps .epx .dwg .dxf.

Google SketchUp
Ruby is a scripting language whose use in SketchUp was first introduced in SketchUp 4. Since its introduction SketchUp users have shown their creativity by creating hundreds of useful tools using SketchUp Ruby.
There is a Hello World Tutorial for Google SketchUp about creating dialog boxes.

Ruby Application Programming Interface (API)

User community
SketchUp users can share their work for free in the Gallery on the SketchUp official website. This gives a place where users can share their work in many fields including, Architecture, Construction, Education K-12, Game Development, GIS, Graphic Art, Higher education, Industrial Design / Furniture, Interior Design, Landscape Architecture, and Mechanical Design.

Gallery
SketchUcation is a gateway to the SketchUp Community. Information on worldwide training locations, Training CDs & DVDs and online training. But also tutorials on the User Interface of SketchUp such as the Tools and Menus as well as a growing number of function-specific tutorial videos or how to model objects. There is also a Blog and a Forum. Coming in the Fall of 2007 is a Game Development subsite. Other sections such as SketchUp add-ons and tutorials on the Panels and VCB will be added soon.

SketchUcation
The SketchUp Components Collection is a moderated collection of SketchUp Components, currently focused on those useful in planning PC modding projects.

The SketchUp Components Collection
SuWiki is a Wiki encyclopedia for SketchUp users. It provides an open environment for SketchUp users to find, and contribute to article and tutorials on the use of SketchUp.

SuWiki
Many users also share their ideas and knowledge about SketchUp and other modeling programs in:

SketchUp Google Group Forum, and
SketchUp Community Forum. Plugins

Google