A perspective defines the initial set and layout of views in the Workbench window. One or more perspectives can exist in a single Workbench window.

Perspectives can be opened either in the same (existing) Workbench window, hiding the current perspective, or in a new Workbench window

Perspectives 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.  

The Workbench defines the Resource perspective by default. This perspective shows views relevant to resource management.

Related reference
Window Menu
Editor Area
Project Explorer View
Outline View
Tasks View