It is one of those "ancient" societies which has a "modern" following. There is no connection between anything today and the original, and the original were not so great either, just a mix of Eastern religions and a belief in "hidden" teachings.
There are many societies which use the name, some are "Christian", some are Masonic, some are other. The "Christian" ones use passages like these:
To whom he said: To you it is given to know the mystery of the kingdom of God; but to the rest in parables, that seeing they may not see, and hearing may not understand.
However, they don't realise the context of that and ignore this:
For there is nothing covered, that shall not be revealed: nor hidden, that shall not be known. For whatsoever things you have spoken in darkness, shall be published in the light: and that which you have spoken in the ear in the chambers, shall be preached on the housetops.
They are sort of like the Kabbalah. A bunch of people pretending to be enlightened and forgetting the most basic revealed truths.