A: These are the trim level designations of the TJ given by Jeep. They are all Wranglers. Basic differences:

SE: 4 cylinder, 5 speed standard, auto option, minimal options from dealer available (no D-44, no 6 cylinder) As of 2003, it is the only model that has the passenger side airbag off switch (due to the rear seat not being standard).

X: Introduced in 2002, it is between the SE and Sport, with the biggest difference being a standard 6 cylinder. Also comes with back seat standard. Still no D-44 axle option though. The "X" is offered in 4 packages, the Apex (2002), Freedom (2003), Columbia, and Willy's (2004) which primarily consist of different seat material, wheels, decals/graphics, and a few more options standard.

Sport: Comes with several standard features not included with the SE and X models. 6 cylinder standard. Has the D-44 axle option.

Sahara: The "Cadillac" of TJ's. 6 cylinder standard. Has many standard features (A/C, Tilt, Cruise ect..), also has the 1" wider fender flares (painted to match body color) and body cladding under the doors. D-44 is available.

Rubicon: Introduced in 2003. According to Jeep, "the mightiest Jeep® vehicle we've ever produced.". 6 cylinder standard. It comes with D-44 axles front and rear standard, has a selectable locker front and rear, a 4:1 transfer case, 1" wider fender flares than the SE, X, and Sport, standard 4 wheel disk brakes, and the largest tires offered on a stock Jeep from the factory (LT245/75R16, which = 30.5x9.6x16).

Unlimited: Introduced as a 2004.5 model. This model is a TJ that has had the frame extended 10" and the overall length by 15". It has a Dana 44 rear axle, 6 cylinder with a 4 speed automatic transmission with 3.73 gears in the axles standard. In 2005, a 6 speed manual transmission replaced the 5 speed. It is also available in a Rubicon trim level.

There are more differences than this. Go the the Jeep Website if you really want to know all the differences.