Classes

Classes in Operations Manager are pretty much templates for the objects, or instances, that you see in the Operations Console. When you discover something in Operations Manager using discovery rules (scripts, registry, whatever) you create instances of the classes you have defined in the management pack using your service model.

It is on these classes you will target your rules, monitors, reports and overrides.

In short; a class is not an object but rather the template from which objects are created.