That sounds technical, the but the upshot is that if you are close to zero on your Gini, you're very equal, whereas the closer you get to 1, the more unequal you are.
The most unequal place in the U.S., in terms of income, is the New York area, at 0.501 (tied with Santa Fe, NM, but representing a much larger population, obviously). That's why Occupy Wall Street picked Lower Manhattan as its first protest site. Although you could also say that they picked it because...well, that's where, you know, Wall Street is.
I know, I know, you're shocked. But wait! LA is also pretty unequal — and not too far behind New York, at 0.483. The point is that the worst places in the U.S. for inequality are also the best places to make a lot of money. The question is, Are the populations in the these regions becoming hoplessly divided into haves and have-nots? And is there really anything that we can or want to do about it?