Mahavakyas, literally -great sayings-, are equations found in the Upanisads of the four Vedas. They reveal that the truth of the individual (atma) and the total (Ishvara or Brahman) is essentially one and the same reality.
Being conscious of himself/herself, a human being experiences self doubt, a sense of inadequacy and insecurity, thus constantly seeking approval from others. Mahavakyas address the human problem fundamentally as they reveal that you are the most significant person. The experiencer/knower (atma) is revealed to be essentially identical with Brahman, the cause of the world, being self-revealing, self-existent consciousness.
In this series of talks held in his ashram in Rishikesh in March 2012, Pujya Swamiji makes us see the meaning of the Mahavakya *Ayamatma Brahma* which is found in the Mandukya Upanisad (1.2) of Atharva Veda.