Styles and Stylesheets
The styles pane to the right or the main editor screen contains all the available predefined styles.

These are taken from the currently selected stylesheet which you can change using the drop down list at the top of the pane.
By using stylesheets and the styles contained in the Styles pane you ensure the look of your website is consistent from page to page. To add your own predefined styles and even add new stylesheets please see the section Templates and Stylesheets.