the first SUVs were simply pickup trucks that had rear seats and a permanent roof in back in place of the truck bed- a step beyond the simple "camper shell." More sophisticated SUVs eventually got their own body styles, although most were still based on a pickup chassis. SUVs were manufactured mainly by the US, although the British made some as well, such as Land Rover.
Following a large increase in popularity around the turn of the century, SUVs began to flood the market. every car company had one, if not multiple, models of SUV. Foreign companies are in on the market as well, most notably the Japanese, and most recently some of the German car companies, such as Porsche and Volkswagen. with the newer models, there are basically three categories:
The "real" SUV- a vehicle that has not lost its roots as an offroader. included in this group the Hummer H1, Chevy Trailblazer, and most Land Rover vehicles. To a lesser extent, the Ford Explorer, Chevy Tahoe/GMC Yukon, and Dodge Durango also fall under this classification.
The "Behemoth"- these SUVs are emormous... in fact, they are so large that taking them offroad is usually a bad idea. The Chevy Suburban (aka the GMC Yukon XL) is a household name and was the prime example of this type of vehicle for many years until Ford unveiled the even larger Excursion. Ford's Expedition is also in this category, and the explorer may also end up here because it gets larger with every redesign. Large SUVs always have 3 rows of seats and typically seat 7 or 8 people. many "soccer moms" have purchased these SUVs as "cool" replacements for minivans, although they have the same passenger capacity but are less stable and less fuel efficient than minivans and even most full-sized vans. the Ford Excusrion gets 10~11 miles per gallon for city riving. The immense size of these SUVs makes them perfect for camping, moving furniture, and towing.
The mini SUV- the last general grouping of SUVs didn't hit the market until the SUVs' surge in popularity. these are primarily based on car chassis and carry 5 people. they are pretty much useless as offroaders and don't get amazing mileage, although this category of SUV has the best mileage of the three. they have much better road manners than other SUVs as well. These SUVs are more numerous than the others because of their price and relative practicality compared to the other SUVs. the Jeep Liberty, Ford Escape, Toyota Rav4, and Mercedes Benz M-class are only a few examples.
There are still more that don't really fit in the 3 categories. Some SUVs exist purely for their "cool factor" and luxury accomodations. these are the Cadillac Escalade, Lincoln Navigator, and Hummer H2.
Others are just unique for their capabilities. the Porsche Cayenne and Volkswagen Touareg are both said to be very nice road vehicles, but they are also capable of handling moderate offroad situations. The Crysler Pacifica is a minivan-SUV crossover that has similar attributes.