I know it's an old thread, but since nobody explained, I will:

Let's say you go test drive a brand new 4Runner. Bright red limited edition. You love it, everyone's happy, and you want to buy it. As the sale progresses, you become the customer from hell from the dealership's point of view. Not happy with the pricing, playing hardball, not falling for the "4-square" and "up to" nonsense, and you've kept them there past closing. It's late, they want you out of there, but they also want the sale. Sales manager says "Fine, we'll go with that price. Let's do it" and sends you home in a bright red SR5 or Sport edition, or maybe swaps you into the red Limited that was used as a demo with 1500 miles on it.

This actually happened to an ex-GF of mine years ago with a Mitsubishi Eclipse. She was the customer the sales staff always saw coming, and could get her into a new car at oil change time just by saying "you know, you've got nearly 25,000 miles on this old car. This is when things start nickel and diming you," and she would freak out and trade it in.
Anyway, she went in and test drove a top-of-the-line Eclipse with all the bells and whistles, made a deal based on those numbers, and drove home in what I called the "rental edition" with plastic hubcaps and "a premium CD player stereo that they threw in for free. Those guys are so nice!" She didn't even realize what happened until the first big rainstorm and she couldn't find the switch for the rear wiper (which was something she liked about the car she test drove.) "Sorry, nothing we can do, this is the car on your paperwork."