With the Compass, you do get more features standard as opposed to many other basic models, including the Patriot. Many will tell you to get the manual shifting unit, and that may net you a little better MPG, but they are hard to come by. Your choice there, I am fine with my wife's CVT.
Sport = No thrills "basic" trim. You have power options like windows and mirrors (heated), but no height adjustment for driver's seat (available as option though) or other similar conveniences.
Latitude = This is usually the sweet spot, and the ones you find the most. Steering wheel audio controls, height adjusting driver's seat, and many other available options like a nicer sound system and navigation.
Limited = Deluxe. Power driver's seat, navigation, etc. etc. As much luxury as you can get in a little Jeep without upgrading to a Grand Cherokee.
They of course come in 2WD (front) units that get the best gas mileage and come with the slightly smaller 2.0L engine, or 4x4 Freedom Drive I, or 4x4 Freedom Drive II. Both 4x4s come with the larger 2.4L engine.
The standard 4x4 FD I system only eats one MPG and is very handy to have if you are heading north. The 4x4 FD II system has different gearing, is really geared for off roading (only thing better would pretty much be a Wrangler), but eats up a lot of MPGs.
I believe the sticker MPG ratings are or somewhere around 20/21/22/23 in town and 23/26/28/29 (FDII CVT/FDI CVT/2WD CVT/2WD Manual).
Thats a quick crash course. Much better if you go to www.jeep.com
and build various Compasses. The site will show you the different options available and what standard options come with the different trim levels.