I'm not sure what level of explanation you want... Most simply, torque is a turning moment. The idea of torque is that if you apply a force at a greater distance, you get a bigger rotation - it would be easier to swing a cat by its tail than its middle (if you wished to swing cats), and it requires less effort to open a door from the edge, rather than at the pivot.
Where ##\tau_{Total}## is the total torque on the body, and is the sum of a number of torques, ##\tau_{i} = \vec{r_{i}} \times \vec{F_{i}}## where, ##\vec{r_{i}}## is the position vector, and ##\vec{F_{i}}## is the force.
The angular momentum of a body is related to the torque applied:
i.e -if we don't have any torque, then the angular momentum must be constant in time. The body cannot be spinning up or spinning down - in cannot be changing its motion in any rotational sense. So in this way, we see that a necessary (but not sufficient! - e.g we also have to balance forces) condition for equilibrium is that the total torques on a body must be zero...
The question is more geared towards when trying to improve stability or how do stability and torque correlate. I was thinking it had to do with Centre of mass or base of support. I have no idea what could be said for ergonomics