Pearly, round, fat, medium-grained Italian white
rice, grown in the
Lombardy and
Piedmont regions of
Italy. (Also cultivated in places like
California and
Missouri).
The key reason arborio is used for risotto is that the kernel is surrounded by a soft starch, amylopection, that dissolves in the cooking process, combining with the stock and making the end result creamy, but with a "tooth" (the center of the kernel stays firm- but only if you add the liquid to your risotto a little at a time).