When Hamlet refers to Ophelia as a nymph, this is an example of an allusion. And allusion is an indirect reference to an object, place, person or idea that belongs to a different context. Usually, the author references this indirectly and it is up to the reader to make the connection. In this case, the reference is to the mythological figure of the nymphs.
False, the author just has to put enough details and opinions in the text, the the audience can feel what the author feels. That is called authors purpose.