In the sentence:
The
story takes place in a steel mill in Pittsburgh.
The
sentence is a fact. A fact is something – news, information, a talk, a seminar,
etc., that is telling the truth and objective. This could be referenced by the
people listening to it. An opinion is a declaration of the person’s thoughts
and suggestions that is possibly subjective in nature. This cannot be
referenced since it is declared by basing of emotions or one’s own perception
on the information.