The value for the outer radius defines the overall size of the disc. A value for the inner radius of greater than zero generates a perforated disc. The inner radius can be no larger than the outer radius.
Disc Segments gives the radial subdivision, Rotation Segments the subdivision along the circumference.
Choose a value from this drop-down list to set the object’s initial orientation in space. This gives you a quick way to turn the object on its axis.