THE DOCUMENT TREE
When a browser loads a page, it creates a hierarchical representation of its contents which closely resembles its HTML structure. This results in a tree-like organization of nodes, each representing an element, an attribute, content or some other object.
Each of these different object types will have their own unique methods and properties. But each also implements the Node interface. This is a common set of methods and properties related to the document tree structure. To understand this interface better, take a look a the diagram below which represents a simple node tree.
The Document Root
The document object serves as the root of this node tree. It too implements the Node interface. It will have child nodes but no parent node or sibling nodes, as it is the starting node. In addition to being a Node, it also implements the Document interface.
This interface provides methods for accessing and creating other nodes in the document tree. Some methods are: