For those who are wondering what esoteric Freemasonry is:
An excerpt taken from 21stcenturyfreemason.com:
The term 'esoteric' is itself a juxtaposition with that which is 'exoteric'. The exoteric nature of Freemasonry is available to anybody who looks into the fraternity and its work, it is the surface layer of teachings and rites taken at face value. These teachings are themselves made clear by merely having a dictionary understanding of the language and taking what is said as it is commonly used. Esoteric Freemasonry on the other hand refers to an understanding of the ritual, history, and practices that lies beyond the surface. It is that which is not revealed unless one delves deeper into the meaning and significance of the words and actions that are displayed. This distinction is not at all unique to Freemasonry, and indeed practically every system of spiritual knowledge (and even many non-spiritual traditions) have both an exoteric and an esoteric component. Judaism has the teachings of the Qabalah; Christianity has various strands of Christian mysticism such as Gnosticism; Islam has Sufism; Hinduism has the teachings of the Tantras. These are just some of the more well known examples, but there are countless more and they all have one major thing in common - which is that they all refer to a level of understanding and insight that can only be achieved through devout dedication and internal reflection.
Therefore, the first thing to know is that esoteric Freemasonry refers to an understanding that lies beneath the surface. It is a path that is walked by each individual as they come to understand the work of Freemasonry and its various components. Through internal contemplation of the mysteries that are contained within Freemasonry, one can arrive at an understanding that sheds light on something much deeper and impacting then the words themselves convey. Although few Masons will say that they are esotericists, once you have started down this path of understanding you are inevitably coming into contact with what is collectively known as 'esoteric Freemasonry'. This itself has many different branches and paths, and Masonic libraries are filled with the different explorations of those delving deep into the mysteries within Freemasonry. Indeed, these paths could be said to number as many as there are Freemasons! This personal relationship with the esoteric in Freemasonry is part of the reason why it is so difficult to explain and discuss - for it means different things to different people.
If you want to pursue such studies for yourself then there is no better place to begin than that which is put right in front of you. 'A system of morality, veiled in allegory and illustrated by symbols' - the first key is given to you right from the beginning. The explicit moral teachings make up a large part of what is exoteric Freemasonry, and they are no less powerful or useful because of it. However, the source of these teachings comes from the esoteric understanding. The allegorical and symbolic nature of our ritual and ceremonial work was intended to allow those who sought it greater insight and relationship with their spiritual component. The exoteric Freemason is concerned with getting things right according to the book - the esoteric Freemason understands why they are even in the book in the first place. It is important to recognise though, that the esoteric cannot exist without the exoteric and vice versa - indeed they eventually are seen to be an inseparable whole. Even if one does not concern themselves with deeper teachings, the esoteric aspects of Freemasonry will still have an effect on you; such is the wonder of the mystery tradition that it often does not even require conscious effort to gain some profit from.
Esoteric Freemasonry begins with the study of our allegory and symbolism, which is something that 99% of Freemasons have sought advancement in. It is here that the inner transformation begins. What at first seems a merely academic work soon takes on a more personal and inspiring tone. At first you spend your time reading about the esoteric insight of others, that which has been found before you. These should certainly be listened to, for one of the great strengths of our fraternity is this vast body of knowledge that has been, and continues to be, passed down through the generations. But what soon emerges is a personal relationship to the Work, the deeper your understanding develops the more fully your own insight and revelation will emerge.
How deep does the rabbit hole go? To use a common turn of phrase. All the way, comes the answer.
The tradition contained within esoteric Freemasonry, like the other forms of esotericism available, allows one to connect with the source of all insight, intuition, and knowledge. This is the creation of the Perfect Ashlar, the triumphant return from The Fall. It is a path that allows one not only to experience a union with the divine, but to return from that experience in order to help uplift the world around you. As our spiritual aspect matures, so does our ability to positively affect the world around us. It is here that the esoteric and exoteric strands of Freemasonry are once more united. For just as the exoteric teachings implore us to be better men, to serve our community and the world in order to improve its condition, so too do the esoteric teachings grant us with the power and inspiration to achieve this to our fullest potential.