An inode (or index node) is something which points to something else, to help you find it easier. In a library, it would be the cards in the card catalog. They help you find a book.
There are 3 layers of inodes in this system: the root node, the medial node, and the distal node.
Each node lists the categories it has, and then tells you where to go to get the sub-categories for that category. Here, for example, you have the root. If you follow the next link under INF, you'll get to its subcategories (REF). If you follow the next link under REF, you'll see DIC, ENC, and MAP. Following the next link under those will get you to sites that contain that particular type of information.
I am building a desktop explorer that makes this much easier.