This document discusses inserting nodes into a circular doubly linked list. It defines a circular doubly linked list as having both doubly linked list and circular linked list properties, with each node pointing to the next and previous nodes and the last node pointing to the first. It presents functions for inserting a node after a given node and inserting at the end of the list, with the latter handling the case of an empty list by making the new node both the next and previous pointer of itself.