The statement they are trying to explain is that "Do not go gentle in the good night" means do not take life or granted live life to the fullest and in the end you will die it is inevitable.
Hope this helps,
kwrob <span />
I think that it would be if someone (or the author) uses a metaphor or a simile.
You should read the book and find out! Tell me if it is a good read and I will pick up a copy for myself!