This lecture was given on the 5th day of the month of Av, the day of passing of the holy Arizal, the greatest of the Tzfat Mystics in the 16th century. In the lecture, Rabbi Ginsburgh gives a thorough explanation of the origins of the concept of the 50 Gates of the sefirah of understanding.
The first source is from the Bible, from the end of the book of Job. The 50 questions G-d asks of Job correspond to the 50 Gates of Understanding.
The second source is from the Zohar, which derives the 50 Gates of Understanding from 50 times that the Exodus from Egypt is mentioned in the Five Books of Moses.
A third, newer source, derived from the teachings of Chassidut is also explained.
These three sources are then corresponded to the 3 foundational categories of the Ba'al Shem Tov: worlds, souls, and Divinity (see also Introduction to The Hebrew Letters).
In the main part of the lecture, Rabbi Ginsburgh goes through the 8 manifestations of the 50 Gates of Understanding as they appear in the writings of the Arizal. Each of these manifestations is explained.
One of the main foci of the lecture is the kavanot (the Kabbalistic intentions) of Keriyat Shema.