Okay kiddo, so Adam the Monk was a man who lived a really long time ago, like over a thousand years ago. He was a Christian monk who lived in a place called Mount Athos, which is a big mountain in Greece.
Adam was very wise and learned a lot of things about religion and spirituality. He wanted to share what he knew with other people, so he wrote a book called "The Philokalia", which was all about how to live a good and spiritual life.
Lots of people read his book and learned from it, and it became very famous. Even today, people still read and study it.
So, in short, Adam the Monk was a wise man who wrote a book to help people understand spirituality and how to live a good life.