Why do you think it is highly cited?

The paper is the first to verify an aspect of a conjecture put forward by Ashoke Sen. The importance of Sen's work is that it suggests possible frameworks (open string field theory) may be useful to treat non-perturbative aspects of string theory. Nonperturbative string theory has been overdue for over two decades, so the conjecture together with the physics it motivates, may turn out to be very important.

  Does it describe a new discovery or new methodology that's useful to others?

The article provides evidence for a conjecture and thus together with the original paper containing the conjecture and subsequent papers verifying other aspects of the conjecture, it does describe a new discovery. The new discovery may prove to be useful to others if it does indeed lead to a better understanding of nonperturbative string theory.

  Could you summarize the significance of your paper in layman's terms?

Open string theory tries to describe the world in terms of elementary building blocks that are (one dimensional) strings as opposed to (zero dimensional) points. The simplest version of the theory, constructed more than twenty years ago, suffers from instabilities that obscure the meaning of the theory. Our paper helps to clarify the origin of these instabilities and helps to show how the theory should be interpreted.