Staying in balance is another of the fundamentals of good climbing technique. Remaining in or as close to equilibrium as possible will save your upper body some energy. With climbing, balance can be the traditional static balance like balancing on one foot. However, it can also include a more dynamic balance when on steep rock or performing dynamic moves, where understanding the secondary effects on the body of moving. In a way, this can be understanding how the climber can swing/pendulum as we move from hold to hold.
For most people, though it will remain the traditional idea of keeping our centre of gravity, over our feet and in doing so reducing the tension in the arms and fingers.