Basically, it's a forced hallucination where you're supposed to choose a knife or a hunk of cheese, and then your choice determines the rest of the test. The results are supposed to tell you which of five factions you belong in--Erudite, Candor, Dauntless, Abnegation, or Amity--each of which value one trait above all others (intelligence, honesty, bravery, selflessness, or kindness). But it turns out the results don't really matter, because you can choose your faction anyway. But the results actually do matter, because Erudite looks at your test results and tries to kill you if you showed traits of more than two factions. The whole "Superman is given powers by an evil star and turns Chicago into a brutal dictatorship where even his calculator (Fortuity) is a serial killer" is a lot more straightforward.