Perspective View

To select the perspective view, click the Perspective tab at the bottom of the view. Perspective is useful for setting elevations, sculpting terrain, adding doors and windows, and other tasks which require a 3-dimensional view. Most editing tasks can be performed in either top-down or perspective view.

See also:

Top-Down View
Realtime Walkthrough
Panning the View
Orbiting the View
Zooming the View
Zooming into the Selection
Picture Import Wizard