What are rules for extending and implementing abstract classes in visual basic?

In Visual Basic, when extending and implementing abstract classes (declared with the MustInherit keyWord), any derived class must provide concrete implementations for all abstract members (methods, properties) defined in the base class. Additionally, the derived class can implement its own members and override base class members using the Overrides keyWord. The derived class itself cannot be declared as MustInherit. When instantiating the derived class, it can be used like any other class, provided all abstract members are implemented.