Home Screen; Extended Home Screen - HTC DROID Incredible User Manual

 Basics

Home screen

The Home screen provides you with a weather clock that shows the
time and weather of your current location. Tap the respective item to
open the associated application.
The Home screen also lets you add the items you want and need
on the Home screen. Add items like application icons, shortcuts,
folders, and widgets to give you instant access to information and
applications. To learn how to personalize your Home screen, see the
Personalizing chapter.

Extended Home screen

The Home screen extends beyond the screen width to provide more
space for adding icons, widgets, and more. There are  "additional"
screens apart from the main Home screen.
You cannot add more screens.