Summary:
Star Wars was a revolutionary science-fiction film that changed the perception of robots in the minds of many from in-human technical apparatus to real characters, with a sense of humor and feelings.  R2-D2 and C3PO are the two main robots introduced in this film.  Their antics set them created a place in the hearts of many children and adults.

Questions

1.  What is the role/function of robot? Why was it created?

C3PO is a protocol droid with specialized programming in droid/human relations and language translation and interpretation.  Among C3PO's standard equipment are visual, auditory, olfactory, and sensory receptors, a broad band antenna for receiving droid transmissions, and a speech vocabulator.  He is fluent in over six million galactic languages.  Due to the lack of periodic memory wipes, C3PO has developed a talent for embellishment.  He is full of himself and and his superior manners with all of the knowledge he's had punched into him.  Tends to be a worrier.

R2D2 is a purely mechanical droid for delivery messages, confidential codes, hardware repair, and navigation assistance.

2.  How human is it? How human is it meant to be?

C3PO is very anthropomorphic but definitely mechanical.  He does not have swift movement of limbs, but can think for himself and undergoes emotions.  He tends to be a worrier.

R2D2 is not at all human in design, yet appears to be completely aware of his circumstances and is insistent on being with his master, Luke, no matter how dangerous the circumstances.

3.  How does it act in society? How do humans react to it?

C3PO and R2 both blend into society and appear to be a normal part of things.  Both are nearly treated as humans, accept for the fact that they are bought and sold as machines.  They are always included in conversation and are spoken to as a human would be.  They actually formed bonds with their master and are an integral part of the Rebel Alliance.

4.  What are the consequences within the context of the world of the work?

C3PO and R2D2 are an essential part of the fabric of the universe within Star Wars. The way they are able to identify and fully interact with their human counterparts allows the audience to feel as though these droids are actually a "part" of the same legend as Luke Skywalker and Han Solo. Both have a significant impact on the outcome of the movie, especially R2D2's transport of the Princess' message to Obi One Kenobi and his flight navigation assistance in the destruction of the Death Star.

5.  What influence did they have on the notion of robots?

Probably one of the most significant influences from Star Wars on the notion of the robot is the widespread use of robots, even beyond C3PO and R2D2, as well as the treatment of the droids as nearly human, despite clearly being machines. They move away from the notion of robots as merely machines meant for harm but are completely benign and loyal.

Here is the basic design for C3PO.