Oujaii Pranayama is the breathing applied throughout the Ashtanga Yoga practice. Breathing through the nose, with the mouth closed, a subtle sound is created throughout the inhale and the exhale. This sound is created by slightly contracting the throat, almost as if you are breathing through a straw. The length of the inhale should be equal to the exhale and when done correctly the breath should resemble the sound of the ocean.
Each movement is linked to an inhale or exhale. This might seem challenging at first as you may need two or three breaths for each asana. If you are a beginner, try not to get too caught up with the breathing, this will come with practice.
By constantly keeping the awareness on the breath, practice will start to feel similar to a moving meditation, offering many relaxing and calming benefits to the body and mind.
Here is a helpful video: