A Doubly Linked List is a data structure where each node has its data, left pointer, and right pointer.
Here, each node has the address of its next node as well as its previous node (except the last node, the next pointer of the last node will point to NULL, which means the end of a node).
Its advantage over the singly-linked lists is that you will have access to the previous node. You can traverse both from left to right and vice versa.