Being familiar with some of the basics is a good thing, even if you're not a car enthusiast.
I can't claim any sort of expertise, I know what it is when I'm looking at it, but can't do a good job of explaining WHY a car is a sedan rather than a coupe- but to get you started-
Coupe--Closed car with two doors, and technically, less than 33 cubic feet of rear interior volume- term usually applies to any two door car with a joke for a back seat.
Sedan- can have two or four doors, has a decent sized back seat and a trunk seperate from the passenger compartment.
SUV- tricky one- the smaller ones are also being called "crossovers" recently- these vehicles can be massive (Hummer, Escalade, Explorer) or quite tiny (Xterra, Forrester)
Typically the have either 4 wheel drive or all wheel drive and the rear seats can be folded down or removed altogether to maximize cargo space.
Sports car- generally more for performance than for comfort, they are usually little, low slung, two door bits of automotive jewelery- fast, responsive, a serious power to weight ratio and I don't want you getting one until you've been driving for at least 10 years.
Trucks- a closed cab, possibly with a bit of stowage space or even a real back seat and an open cargo area in the rear- other than the closed cab and open bed, there is a lot of variation in trucks- they come in 2 and 4 wheel drive, can be small, medium, large or freaking HUGE, and often have optional suspension upgrades to maximize towing capacity- I LOVE my truck.
AutoTrader.com offers this glossary It is a little "in depth" but you might find it interesting.