Ashtanga is rooted in what is called Parampara.
Parampara is a Sanskrit word which means direct experiential sacred knowledge which is transmitted from teacher to student in succession. Much like the idea of lineage.
A student must spend many years with an experienced guru before this knowledge is transfered. Yoga as a sacred knowledge should be passed down from within paramapara. When the teacher or Guru believes that the student is ready to teach they in turn give the student the blessing to share.
The Ashtanga Yoga System is an ancient yoga system which was taught by Vamana Rishi in the Yoga Korunta. These teachings have been passed down from Guru to Shisha (student) throughout time. We can trace back our lineage as far back as Rama Mohan Brahmachari, who imparted this knowledge to Sri T. Krishnamacharya in the Himalayas in the early 1900s. He in turn imparted this knowledge to Sri K Pattabhi Jois. Sri K Pattabhi Jois spent over 70 years of his life dedicated to teaching this practice, and since the 1960s has taught hundreds of students who were coming to visit him from around the world. His grandson R. Sharath Jois lived with him and began playing around with yoga since he was seven. Sharathji began his serious yoga studies at the age of 19. He spent around 20 years practicing and assisting his grandfather. When Pattabhi Jois died in 2009, Paramaguru Sharath Jois became the director of KPJAYI (Shri K Pattabhi Jois Ashtanga Yoga Institute). He dutifully continues to share the knowledge with thousands of students who flock to see him every year in Mysore India.
Students who have been given the blessing to teach this Ashtanga Yoga system by KPJAYI have received what we call Authorization or Certification by Sri K Pattabhi Jois or Paramaguru Sharath Jois. Students who have received this blessing have spent many years returning to the source in Mysore and continue to do so working diligently with their guru. Authorization Level 1 means the teacher can teach Primary Series, Level 2 means they can teach intermediate series up to where they practice with Sharathji and Certified means they can teach Third series / Advanced A.
A teacher who is certified has been returning to KPJAYI for a minimum of 10 trips (usually many more) and has completed the Advanced A (Third series) at the school.