Each Workbench window contains one or more perspectives. A perspective defines the initial set and layout of views in the Workbench window. Within the window, each perspective shares the same set of editors. Each perspective provides a set of functionality aimed at accomplishing a specific type of task or works with specific types of resources. For example, the Java perspective combines views that you would commonly use while editing Java source files, while the Debug perspective contains the views that you would use while debugging Java programs. As you work in the Workbench, you will probably switch perspectives frequently.

Perspectives control what appears in certain menus and toolbars. They define visible action sets, which you can change to customize a perspective. You can save a perspective that you build in this manner, making your own custom perspective that you can open again later.  

You can set your Workbench preferences to open perspectives in the same window or in a new window.

Workbench
Editors
Views

Opening perspectives
Opening views
Changing where perspectives open
Specifying the default perspective
Switching between perspectives
Configuring perspectives
Saving a user defined perspective
Resetting perspectives