The Center tool specifies a point on a model as the center of the current view. It also changes the target point used for some of the navigation tools.
With the Center tool, you can define the center of the current view of a model. To define the center, you drag the cursor over your model. A sphere is displayed in addition to the cursor. The sphere indicates that the point below the cursor in the model will be the center of the current view when you release the mouse button, the model is centered on the sphere.
The point defined by the Center tool provides a focal point for the Zoom tool and a pivot point for the Orbit tool.