What is the meaning of Torque? How it is calculated? It should be High or Low?

Torque is the rotational equivalent of force.

It is measured in Newton.metres

One Newton.metre of torque is one Newton acting perpendicularly to a one metre arm turning a central axle.

Torque, also called moment or moment of force, is the tendency of a force to rotate an object about an axis, fulcrum, or pivot. Just as a force is a push or a pull, a torque can be thought of as a twist.

Loosely speaking, torque is a measure of the turning force on an object such as a bolt or a flywheel. For example, pushing or pulling the handle of a wrench connected to a nut or bolt produces a torque (turning force) that loosens or tightens the nut or bolt.

The terminology for this concept is not straightforward: In the US in physics, it is usually called "torque", and in mechanical engineering, it is called "moment". However outside the US this varies and, in the UK for instance, most physicists will use the term "moment". In mechanical engineering, the term "torque" means something different, described below. In this article, the word "torque" is always used to mean the same as "moment".

The symbol for torque is typically τ, the Greek letter tau. When it is called moment, it is commonly denoted M.

The magnitude of torque depends on three quantities: First, the force applied; second, the length of the lever arm connecting the axis to the point of force application; and third, the angle between the two. In symbols:

T = r X F

T = rF sin theta

where

τ is the torque vector and τ is the magnitude of the torque,

r is the displacement vector (a vector from the point from which torque is measured to the point where force is applied), and r is the length (or magnitude) of the lever arm vector,

F is the force vector, and F is the magnitude of the force,

× denotes the cross product,

θ is the angle between the force vector and the lever arm vector.

The length of the lever arm is particularly important; choosing this length appropriately lies behind the operation of levers, pulleys, gears, and most other simple machines involving a mechanical advantage.

Nicely explained agent 2706. In addition it is better more torque (high), BUT...But, the problem is in transferring torque from crankshaft to the wheels. All those elements that conduct force from pistons to the wheels must withstand higher torque, so you shouldn't exceed the hardness of the weakest element there or else you might end scratching your head in the middle of nowhere. Usually there's some reserve in persistence all those shafts, tooth wheels, bearings, axles, joints, etc so you can add some power to the machine but do not exaggerate.