My best understanding of it is that it consists of a loose affiliation of people with criminal minds. Though it’s woo-woo to say this: Off-world influence has also been observed. Their only real power is their willingness to perform criminal acts (starting with their current favorite – character assassination) to get what they want. In the past it was thought that they mostly indulged in blackmail, and that may still be true. The stories are pretty grim. But we all know that people really do do this to each other.