You can customize two areas of your websites/sites in this Content tab area. To get here, go to Admin > Sites > [Select Site] > Settings > Content tab. The first is the Contact Block and the other is the Footer area.
Contact Block - Add a block of information that will be used in a certain places of your site depending on the skin you choose.
Footer Content - Enter text or images to appear in the footer of each page of your site. Once you add information in this area it will appear on every page.
Below you can see an example of these two areas: