The Design panel is the control center which allows you to make design changes to your site. When you select Design from your Dashboard navigation bar, you will see the Design panel on the righthand side of the screen. View the support video below for an in depth overview of the Design area of your Dashboard.
There are only two tabs in the design panel: Sitewide and Page.
Sitewide changes affects every page that is visible on your website.
Page changes only affects the specific page you are currently viewing in the Design tool.