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 in one of three ways:
in the same (existing) workbench window
in a new workbench window
in the same window, replacing the current perspective
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.
Here is an example of a perspective: