A small work-oriented compartment formed by a desk and a chair. Study carrels are most often found in libraries. They are, in short, available workstations: miniature versions of your desk at home, in your office, or what have you. Study carrels provide a place to sit and leaf through your stack of research to see what's applicable enough to check out. They give you a place to collapse under the weight of this whole school business. They give you a place to, of all things, study. You can sit here studying for hours and hours and get up and get a Diet Coke and a Snickers bar and come back and study some more. You need no sleep! NO SLEEP!
Study carrels are designed to keep you from distraction (and sleep). You the hell study in them. You work. The only distractions are those provided by previous users in the form of marginally interesting graffiti. They are otherwise bare. You have a desk, a chair, a little shelf, and adequate lighting. You might get a door, by means of which you can shut yourself into an actual compartment as opposed to a partially-walled area. You might get a window, if this is how the carrels in your library are placed, but this is an unnecessary and possibly harmful thing; being able to see the outside world can be the most distracting thing about this kind of carrel. You could be out there! But instead you are in here, functioning as a purely academic unit.
The desk is bounded by walls, both before you and to either side. The chair is hard, wooden, uncomfortable and overly varnished. The light is generally fluorescent. You have only one thing to look at: your work. You have one thing to do: work. You are bounded by the walls of the carrel for the duration, and so function according to its rules. You force your eyes open, force your cramped hand to write more notes. You rake your fingers through your hair, staring at the problem in your notebook and your three potential solutions, none of which worked. You drink your Diet Coke, gone lukewarm and flat, but you don't really notice, or at least don't pay attention. You are working; you concentrate.
For this reason, study carrels are very useful. Easily distracted people will find no distraction, no interruption until the library blinks the lights 15 minutes before closing time. Those prone to falling asleep while studying will find the seating arrangement relatively inhospitable (although after a certain point, if you are going to sleep, you are Going to Sleep, and not much is going to stop you). People with no good workspace of their own can adopt this one for a little while, or a long while. It is an environment designed solely for work, an environment to which it is easy to acclimatize. Anyone can work in a study carrel. Anyone does.