Each Eclipse PDT window contains one or more Perspectives. A perspective defines the set of views and their layout, in the PDT window.
Within a window, each perspective shares the same set of editors.
Each perspective provides a set of functionality for accomplishing a specific type of task or that enables working with specific types of resources. For example, the PHP perspective combines views that you would commonly use while editing PHP source files, while the Debug perspective contains the views that you would use while debugging PHP programs.
Perspectives define the types of information that appears in some of the 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 open perspectives in the same window or in a new window.