Regions are different sections of a design that you can design independently. Most designs have two regions, the Front and the Back. Folded designs may have more regions. For example, a folded business card has three regions, the Cover, the Inside Cover and the Inside.
When a design is created, its Primary Region is initially displayed. The primary region is the region that normally has most of the information on it. On most designs this is the Front region. On some folded designs it can be the Inside region or some other region.
You can easily switch regions by selecting the appropriate tab above your design in the main window.
Each region is designed independently and when you choose to print they are combined and printed in the proper location and side of the stock.