What does it mean for a non generic class to extend a generic class

Question

public class B extends C  {

}

What does this mean? That C needs to extend A? What extra restriction am I putting instead of just saying B ext

Answer 1

In simple words

That doesn't mean anything, unless there are some methods defined in Class C or its ascendants, to either accept or return Type A parameters.

By doing so you are ensuring the Type safety by imposing restrictions saying "They can accept or return objects of Type A".