All right, now this is a little complicated but I'll try to explain anyway. I had quite a bit of trouble grasping this at first too (stupid GM with their constant name juggling and model switching )
I'll try and add pictures to better help you understand

Ok, so for 1977 GM "downsized" all their full-size cars, which basically means they redesigned them and the cars were much smaller than they were before (about a foot shorter and 800 pounds lighter).
This "downsizing" resulted in the "box-body" Chevrolet Caprice we all know and love, along with it's Buick, Olds, Pontiac, and more importantly, Cadillac siblings.




The new downsized Cadillacs were known as Deville or Fleetwood, depending on the trim. But the more important part is that at this time both the Deville and Fleetwood were THE SAME CAR, minus a few options that differed from model to model.




This continued until 1985, when GM downsized their cars AGAIN, making them even shorter and lighter than the preveious "downsized" models.

"downsized" Olds 88


Unfortunately, these TWO rounds of downsizing (the first in 1977 and the second in 1985) resulted in tiny "full-size" cars that were about the same size as the compacts of only a few years ago! Keep in mind that even though I call them "tiny" they are still very large by European standards

The Fleetwood I took a picture of is an example of one of these "tiny" full-size cars that were "downsized"


Ok, now I get to the complicated part, the naming of the cars

Now, when GM downsized their full-size cars again in 1985, they decided to keep around some of the older, bigger models to sell alongside the new downsized, smaller ones.

The only big, old models they decided to keep were the Caprice, and the Fleetwood (both of which continued until 1996, with a redesign in 1991, but of course you know about that ). Also note that GM decided to keep around station wagons models of the big, older full-sizes, one for each division (Buick, Olds, Pontiac, Chevy)

So, Cadillac decided to swith the names Deville and Fleetwood to the newer, downsized model (the one I took a picture of).

However, they decided to name the older, bigger model that they still kept around the Fleetwood Brougham which in 1987 simply became Brougham (leaving all the Fleetwood nameplates to the newer downsized model)

So, in summary, between 1987-1992, if you wanted a full-size Cadillac you could purchase one of two models:

-The smaller "downsized" Fleetwood/Deville (like the one in my picture)




-Or the bigger, traditional Brougham (like the one the guy bought in the Top Gear American Special)




Keep in mind these are VERY different cars, and much more than just trim differences