Parent Categories and Sub Categories are used to organize your Questions and Tests.
Create and manage your Categories under Tests > Categories page, or create new Categories on the fly wherever you see a 'New Category' link.
Tip: Categories are particularly useful when you want to create a Test using Randomly selected Questions.
Adding Randomly selected Questions means Questions are automatically selected from specified Categories within your Question Bank. Each time the Test is taken, a different set of Questions is displayed.