The word esoteric, which acts as a qualifying adjective for the phenomenon of esotericism, comes from the Greek term esoteric which means in other words "internal knowledge" in the sense that it is secret or little known in a public way. The esoteric adjective is normally used to designate some religious practices, groups or forms of sociability that precisely involve keeping secret what makes up the community and its knowledge. 
Esoteric is understood as that which is part of a secret knowledge that is only known or learned by a select minority. That which is kept hidden and revealed to a select group
In antiquity precisely, the philosophers, communicated their doctrines and ideas to their disciples only.
Esotericism: set of knowledge and practices that are professed by a sectarian minority
Esotericism consists of a series of knowledge, teachings and doctrines, traditions and rites that are followed by a sectarian group, which are kept secret, that is, they are known by a few, that is, the members of the group and nothing else. They will be transmitted only to the initiated.
In ancient times it was quite common for a school to spread a doctrine for all and on the other hand keep other knowledge secret, reserved for a few.
Those who could know these doctrines were chosen and by case it is that there were many that were partially known or decontextualized.
Esotericism in Ancient Greece
In Greece, for example, esotericism was a teaching that was taught in schools and was not accessible to everyone as it was with teachings that were carried out in the open air.
Thus, the disciples of one of the most relevant Greek philosophers such as Pythagoras were divided into exoteric and esoteric, the former were simple students, while the latter enjoyed the knowledge of the Pythagorean doctrine that had been taught by Pythagoras himself.
Plato also made this distinction and then some teachings that he considered to be more technical he reserved to a special and intimate circle.
Among the unique conditions that surround esotericism, we can highlight the secrecy, the oath imposed by many doctrines of not being disclosed; and the transmission of knowledge was from teacher to disciple by the oral route.
Negative conception, due to its association with magical practices
On a social and popular level, the idea of esoteric always supposes a negative charge. This is so because when we speak of esotericism, or we say that something is esoteric, we are referring to something that is known by a few, that most of the population does not know or does not understand very well what it is because it is from difficult to understand.
On the other hand, the idea of esotericism is always linked to religious or magical practices, which, because they are not considered legal or official, must be carried out clandestinely, limiting the number of people who know them and who can participate in them.
Thus, examples like black magic, witchcraft, secret societies, lodges, and sects are all examples of esotericism. However, there are also many practices at the eastern level that are considered esoteric because their execution falls on a select minority but that are not considered dangerous or harmful like some of those just mentioned.
Esoteric practices, many times, are carried out in parallel to the official religion that is professed, such as Christianity. In this sense, despite being clandestine, some of these activities are used by many believers who, although they believe in a monotheistic religion, often resort to some practices that they consider to be more direct or effective to resolve some situations in their personal lives. when it comes to solving your problems or anticipating them, such as tarot, astrology, divination, etc.
It is not enough for all of them to pray and that what they want is finally fulfilled ...
Of course, religions such as Christianity are on the opposite side of the aforementioned activities and do not endorse them in any way.
For this matter is that the faithful or believers hide to carry them out so as not to be excluded or singled out.
