OK heres some history points in a nutshell
(hehe i'm doing my art hmk right now, with the question "artists have had many roles throughout history" analyse...with plates etc)
Start with a summary on the traiditonal role of artists. That is, they created artwork to document people, places and events, cause there were no cameras and other technologies etc. Their intention was to recreate images as "realistically" as possible although they often potrayed these things as idolised and glorified scenes.
(there were also rules about how to create things realistically and colours that were "acceptable" etc look up "academies")
After this dah di dah...the camera was invented changing everything. there was no longer a need for "documenting" things through art. So the role of the artist changed and so did their intentions...This whole era as a whole is "modernism". but different "movements" in modernism had different intentions... eg
Impressionists: wanted to create the impression of scenes as they actually were. Which included the added element of time, change and movement. The "fuzzy" brush strokes were instead to give the impression of movement etc.
Cubists: Influenced by technology and faster moving transport such as the train...Wanted to capture things such as movement therefore they "fractured" the picture plane (created jagged effects) with the intention that this show'd images from multiple viewpoints at the one time
Anyway i wont go in detail through all the movements, and you dont have to in this essay either. It is however a good idea to understand the basic philosophies behind a number of key movements (such as impressionism, cubism, futurism, abstract expressionism..."modernism" as a whole) The question wants you to be able to show what the role of the artist has been in various times, what were their intentions and what influenced these (technology, cultural events etc)
http://www.huntfor.com/arthistory/ (click on different eras and most of the "isms") the late 19th + will be most helpful
http://www.arthistory.cc/index_ns.html
Good luck
