The "rack" that they are referring to is the steering rack. It is what changes your turning motion at the steering wheel to the back and forth motion to turn the wheels. The proper name is "rack and pinion steering gear", named so for it's construction (kinda technical to describe and I don't think that is what you are looking for).
Here's a link to a simplified veiw of a steering rack:
Here's a simple little blurb on steering racks:
Here is a more detailed explaination of the Intrepid rack, this is for a first generation Intrepid, but they are essentially the same layout as a second generation:
Even if you don't want to or can't fix it yourself, this info should at least make you an informed consumer.
A sway bar is usually a solid metal bar that connects the left and right suspension to each other. It exists to help eliminate the rolling or leaning that you get when cornering. As the body leans into a turn it twists the sway bay and pushes the car back to a more level position. Bigger bar = less body roll = slightly rougher ride.
Here's a little blurb on sway bars:
What do you mean by not tight enough? Is there a lot of slop as you turn the wheel? Ie: there is movement in the steering wheel before the tires move.
If this is the case it could be tie rods (they connect the "rack" to the wheel steering knuckles) worn rubber bushings on the rack where it attaches to the body, loose clamps or excessive play in the rack itself. I would put my money on worn rubber bushings in the inner tie rod ends or the rack attaching clamps, check out the allpar link above for a picture and description. Just remember that these are big family style cars and some play is not unusual, they're not meant to be "tight" like sports cars but not loose to the point of control problems. Although they do quite well considering the size and intended use of the vehicle.
No matter what, your vehicle should not wander around, especially when you are changing lanes or doing emergency avoidance manuevers. Get it checked out by a professional if you are not comfortable. We're talking about you, your fellow motorist's, and pedestrian's lives here!
PS. No need to be sorry about asking questions. That's how you learn, not everyone remembers that they had to start somewhere too. I applaud your initiave and courage to ask rather than be "in the dark". If anyone gives you guff for asking "simple questions", just ignore them. They've just forgotten that there was a time they were asking the same questions. Take care and drive safe!