Bends are rear shoes with 1/4" (typically) cleat like protrusions on the ends that are employed to provide better traction. They are a watered down form of the now illegal turndown shoes that had been employed with much success in NY (and elsewhere).

There are a number of front and rear shoes that can be uses of race day to provide better traction (however not all trainers employ them, and some even suggest that they are increase the liklihood of a breakdown).

For a more in-depth treatment of a very interesting topic see

http://www.victoryracingplate.com/home.html