Components
Content Components are chunks of html that are dynamically generated and inserted into Content Locations. Each content component can be edited, dragged, or removed dynamically using the Component Toolbar. Here is a list of content components that can be styled - click a logo for more information:
Available Components
Although your Website Builder theme will work if you do not apply any css styles to the html for the optional content components, you will need to style them if you want to give them a unique design rather than the default style that is applied.
Want to see these components at work? An example site has been set up to display them all at http://builderexample.com