In physics, torque is a vector quantity analogous to force in a linear system. Torque = Force applied * distance from axis of rotation. Like force, for no acceleration to occur, net torque must be equal to zero. The relationship that torque has with angular acceleration is given by Tau = I * alpha, where tau is torque, I is interia, and alpha is angular acceleration.

Torque occurs when a force is applied perpendicular to the an object's axis of rotation. The best example I can think of off the top of my head is a wrench. If you apply a downward force, F, on the far end of the wrench, d units away, the torque of the system will be F*d, which gives you the the wonderful unit of torque known as the Newton-meter, N*m (do not confuse this with the joule! The joule is a scalar quantity, while the N*m is a vector quantity). In this case, if the rotation were counter-clockwise, torque would be positive, and if it were clockwise, the torque would be negative (actually, it doesn't matter what sign you associate with clockwise and counter-clockwise as long as you are consistant, but the prior notation is generally accepted). If you ever decide to take a physics class, you will become very acquainted with torque, as many practical problems stem from its knowledge.