Pratikriyāsana or opposite action postures have counterpostural, compensational and transitional roles and are applied at specific points in the practice in order to maintain a sound physiological and psychological base.
This principle has an important role in how we link the different aspects of the Āsana practice, how we close the practice or how we integrate the Āsana element of the practice into other aspects of our Yoga practice.
There are specific guidelines around how they can be integrated into the practice, the first of which is that the counter posture needs to be mastered before a particular Āsana is attempted.
This principle is especially important when attempting to integrate more complex Āsana such as Bhujaṅgāsana or Sarvāṅgāsana into our practice.
On this point you may wish to refer back to a previous post around the question, how do we know that a student is ready to attempt a more progressive posture such as Sarvāṅgāsana?