According to en.wikipedia.org

SketchUp is a 3D modeling program designed for professional architects, civil engineers, filmmakers, game developers, and related professions. Sketchup may also be used 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.