What is the essential knowledge
The essential knowledge is the one of the will of the Creator and His ways of guidance in this existence, as explained in the Kabbalah. The other writings explain in the least details “how” to do, but only the Zohar and the Kabbalah explain to us the exact reasons, and effects of all our prayers and actions.
I believe that most yearn to serve at their best the Creator, but have been accustomed to execute and not seek further, or were kept away from this knowledge. It is now time to know and learn and make known this magnificent science, as it is written and recommended .