also applying there, their application form is awful IMO
Are you referring to the essay for this? http://grad.uic.edu/pdfs/grad_appt.pdf
My guess is that this essay would be more tailored to the TAship/RAship/fellowship you're trying to get. For example, if you're applying for a TAship, elaborate more on your past teaching experiences than you did on your personal statement.
Although the directions on the form don't really state that, and just seems like they want a redundant personal statement... (maybe other programs don't require personal statements) This essay does however have a word limit, which the statement does not.
Sorry if that's not helpful--I am curious now too. Someone help us out!