Who is Bill Oliver, and what does Biff hope to get from him?

In the play Death of a Salesman, by
Arthur Miller, the character of Bill Oliver is an old supervisor for whom Willy Loman's
son, Biff, used to work.

As part of the Lomans' tendency
to imagine situations that they, later on, believe to be real, Biff lives under the
assumption that he is Bill Oliver's best employee and that, in fact, he is a type of
partner of Bill Oliver's business.

This is why Biff goes to
Bill Oliver to ask him for a loan of $10,000 that would be put towards a down payment
for Biff and his brother, Happy, to start a business together. However, during the
restaurant scene of the play, we encounter Happy and Biff discussing that Bill Oliver
does not even remember Biff when he sees him.

This is the
moment when Biff realizes that his life has been a foolish illusion. This is also the
moment when he feels it is time to stop the fantasy under which the Lomans continue to
live and he decides to confront Willy with the truth about it
all.