Atmajnana is not a concept.It is becoming aware of what I am in my real nature just as we are aware of or experience when we are hungry, angry, sorrowful, happy etc.
But there is a difference.The erroneous “l” who is aware of becomes extinct in Atmajnana.
Unfortunately it has become difficult nowadays to find the exact nature of Atmajnana and the description of Moksha(liberation).
The clarity of goal and the role of means (sadhanas) is indispensable to progress on the path of liberation.
These 16 videos will give you very clearly what, how, when, why, how long etc. of this Vedantic pursuit thoroughly corroborated by Vedanta-Pramana.
This is what Sampradaya beginning from Adiguru whether Sashiva or Narayana says.