Roast vs Body vs Acidity Coffee flavor is often described in terms of:


Roast darkness (light to dark)
Body (medium to heavy)
Acidity (smooth to bright)


I have a vague understanding of some of these, but am unclear especially on body. Could someone explain these a bit and show how they differ from one another?
I'm not really an expert, but in basic terms:

Roast darkness: 


Roughly how long was the coffee roasted, much like toast, a longer roast usually brings about a darker flavor. Darker roast coffees tend to have a slightly burnt caramelized flavor.


Body:


I usually think of this as more of a texture than a flavor, probably more easily noticed at the extremes. A "full bodied" coffee sort of coats the tongue causing the flavor to linger while "medium bodied" coffees tend to be a little lighter with a cleaner finish.


Acidity:


Acidity is basically what it sounds like, lower acid coffees are often referred to as "smooth" and higher acid coffees referred to as "bright".


Now as mentioned in the comments these terms are really painfully relative, and somewhat rendered meaningless by an onslaught of advertisers claiming that their coffee is "smooth dark and full-bodied" regardless of the real characteristics.