This is one of the most-misunderstood areas of Freemasonry and, hence, where many of its detractors tend to focus their efforts on discrediting the Fraternity. Masonry is not a “Secret Society” but a “Society with Secrets”. These secrets can best be classified into two categories with the possibility of one other:
1. The Signs, Words and Grips
The first group of secrets includes the signs, words and grips (handshakes) which represent certain aspects of the degrees. These enable Masons to more easily retain lessons taught in the ritual and to identify each other. Although many of these can now be easily found on the internet, they would serve little use, unless one was interested in Freemasonry. They serve a significant symbolic purpose, but not so much a practical one, to modern Masons. These modes of identification did, however, serve a very significant purpose to the European Operative Stonemasons and other forbearers of Freemasonry. It allowed them to recognize one another when traveling abroad and maintain trade secrets. This secrecy also provided for the freedom of thought, speech and religious beliefs within their ranks at a time when these basic freedoms were not widely tolerated.
2. Spiritual Mysteries
The second group consists of the mysteries to be found within the lessons of Freemasonry by those who study its meaning and meditate on the deeper significance. Like The Bible and other great works, there are multiple layers of understanding to Masonic Ritual. There are many opportunities to study these individually or through related Masonic bodies like The Philalethes Society, The Ohio Lodge of Research, The Lodge of Arts and Sciences, The Allied Masonic Degrees, and others.
3. The Great Guardian
The third possibility has received much attention in books and movies for its entertainment value, i.e., that the fraternity serves as a repository or guardian of some arcane knowledge or artifacts, or the home of a hidden power-wielding group. Personally, it would not surprise me to learn that there is some truth here. It could be logically argued that the opportunity and means are there, and I can think of no others better suited for such tasks. But this topic remains nothing more than conjecture and speculation.