One of the most exciting features in SketchUp is undoubtedly the Components. Click on Windows -> Components to view the Component Browser. Open the folder called 'Sampler'.
This folder contains a number of components that you can use inside your 3D drawings. Simply select a component in the browser, then click anywhere within your drawing to place the component at that spot. You can move, rotate and resize these components using the 'Move', 'Rotate' and 'Scale' tools respectively. SketchUp comes with the default Sampler folder which you can view in the Component Browser.
Visit http://www.SketchUp.com/?sid=38 to download a complete selection of component libraries. Some of these libraries are quite large (the biggest one is 16MB), but well worth it. Once you download all the libraries and follow the setup instruction, you can view the libraries as a folder in the Component Browser.
Besides these downloadable libraries, you can also use the 'Get Models' tool. You need an internet connection for this tool to work. Clicking on the tool opens up Google's 3D Warehouse. A host of components that have been built by other users like you and uploaded to the warehouse. Here you can find anything from simple looking tables, to complete buildings with interiors. This is a good place to browse through to get a sense of what SketchUp is capable of doing.
You can also create your own components and groups within SketchUp. I will take you through creating your own component when we look at modeling wind chimes. But for now just know that groups and components are similar conceptually. You can create groups of objects when you want to move them collectively, or to create a copy of a set of items and objects.