Nobody that knows the real answer is going to give it. Not because of mysticism, etc. But because Freemasonry is a charitable fraternity and like all fraternities and sororities, to become a member is of significant intrinsic importance. It is something special and to openly discuss it takes away from the moral lessons learned, the brotherhood created and the experience of becoming a member, etc.
The only real answer comes from being a Mason.
I see your Catholic devotion, so I would compare it to somebody asking you about the trinity or understanding a relationship with Jesus. You could tell them what it's like, but in your heart and mind you know they would only truly understand if they had faith.
So, you'll likely receive a number of answers but I think you can understand my analogy.
Freemasonry has been around hundreds of years. We built your Catholic Churches. Our secrets our out there, but they are misinterpreted, incorrect or not fully understood because to understand them means experiencing them. I've bought books on "Freemasonry". I watched the "entertaining" but inaccurate television programs. I've went to the conspiracy web sites. It's very entertaining, but at our core we are good people who do good things and help each other and our families be better people. We donate lots of money and time to good causes. We are pillars of our communities. The Shriner's are also Mason's and nobody thinks unkindly of a Shriner.
Some Mason's will talk about things they really shouldn't out of respect and their word, but in my opinion any Mason who talks about those things doesn't understand them enough to really "get it". So if somebody talks, we are let down but we also know to really know means to respect the Fraternity. As a Catholic I'm sure you know plenty Catholic who have it wrong as well.
If a man does not have his own word, then he has nothing. We give our word to keep experiences within the fraternity which adds great value to becoming a freemason. Knowing that the everybody who becomes a mason went through the same things and gave the same word is a very proud and bonding feeling.