What is SketchUp?

Overview
SketchUp is a 3D modeling program created and designed for all trades of the construction industry and entertainment related professions. Through the use of simple vectors and planes the goal of the software is to be more intuitive, flexible, and easier to learn and use than other 3D CAD programs. The intent is to equate to a pencil [or study model], use simplicity in commands and have quick visualization capability.

Currently a Google Owned Software, SketchUp features interface with products such as Google Earth, 3D Warehouse, Layout, Style Builder and several other plug-ins.

History
SketchUp was founded and developed in 1999 by @Last Software in Boulder, Colorado and was released in August 2000 as a general purpose 3D content creation tool. Having won several awards in its first year, it found a market in architecture and building design. Its success and attraction was primarily in the fast learning curve process, which allowed for a shorter learning period than other commercially available 3D tools.
In 2006, Google acquired @Last Software. At that point, SketchUp had developed a plugin for Google Earth and had now become a catalyst for new software to develop, such as Google SketchUp LayOut, Google 3D Warehouse, LayOut 2, and dynamic components that respond appropriately to scaling and enhanced Ruby API performance.

Google SketchUp and SketchUp Pro
In 2006, Google announced a free download software by the name of Google SketchUp, which, at the time, was a free version of SketchUp Pro 6. There are few differences between the two, but significant nonetheless. The SketchUp Pro Version export capabilities are extensive and include .3ds, .dae, .dxf, .fbx, .obj, .xsi, .wrl and .kmz, which allows strong compatibilities with other 3d modeling software. Google SketchUp, however, has had limited 3D and vector based export capabilities (.kmz, .bmp, .png, .jpg, .tif), but it includes integrated tools to be used with Google Earth and the Google 3D Warehouse.