The Zoom Window tool is used to zoom in on a selected area of your model. To create a window on an area of the model, click on the Zoom Window toolbar icon and move the mouse cursor to a corner of the window you want to create, then press the left mouse button and keep the mouse button pressed as you drag the window, when you release the mouse button, the view will zoom to the extents of the defined window.
Alternative ways to access the Zoom Window command are:
Note: the Zoom Window operation works best if the 2 corners selected to create the zoom window area are both on the part of the model you wish to view. If either of the corners selected are outside the model (e.g. on the white background or in distant parts of the model) then the operation can have unintended effects when applying a subsequent Orbit command where the centre point of the Orbit operation is in the far distance.