Who is Farm Boy/Westley/Man in Black/Dread Pirate Roberts from The Princess Bride and what is their importance?

Westley is considered the hero of the story. Although, like Buttercup, the reader truly wonders about Westley's heroism. Westley is an evolving character who undergoes several transformations. In the beginning he is the simple farm boy considered illiterate and good for nothing more than slopping animals. There is something captivating about Westley that even the Dread Pirate Roberts cannot ignore. Under Roberts' tutelage, Westley matures into the heroic Man in Black.