When you select the option for canned demo data, you are choosing to work through the application using completely canned demo data.

The canned demo data is built around a distributor of winter sporting equipment, skis and snowboards specifically.

By default, you’ll get 3 basic items.  In addition, if you selected lot tracking, 3 items are created.  If you select Serial Tracking, 3 items are created.  If you select Expiration Date Tracking, 3 items are created.
 If you selected multiple UOM’s, there are 2 created.  An EACH and a CASE.  CASE UOM consists of 10 EACH.