Object Properties
Define the size of the plane.
You can set the level of subdivision separately for the width and height. This is especially useful when you intend to convert the plane to polygons and edit it further. The more segments you use, the more smoothly you will be able to apply tools such as the Magnet.
Differently subdivided, deformed planes.
These options define the direction in which the object will "point". Using these options it is easier - and faster - to rotate the object (without rotating the object coordinate system as well).