As you know (and if you don't know, you can read the documentation about it), a class helper is a type that can be associated to a class. When a class helper is associated with another class, all the methods and properties defined in the helper are also available in the other class and in its descendants. Helpers are a way to extend a class without using inheritance. However, it is not the same thing as inheritance. In other words, if the TFooHelper helper is in the same scope as TFoo, the compiler's resolution scope then becomes the original type (TFoo), plus the helper (TFooHelper). So, if the TFoo helper defines the DoSomething method and the helper of TFoo defines DoAnotherThing, when TFoo is used in the same scope as the TFooHelper, then the TFoo instances, and all its descendants, have also the DoAnotherThing method.