A NodeFilter interface represents an object used to filter the nodes in a NodeIterator or TreeWalker. They don't know anything about the DOM or how to traverse nodes; they just know how to evaluate a single node against the provided filter.
The Document Object Model (DOM) is a programming interface for HTML, XML and SVG documents. It provides a structured representation of the document as a tree. The DOM defines methods that allow access to the tree, so that they can change the document structure, style and content. The DOM provides a representation of the document as a structured group of nodes and objects, possessing various properties and methods. Nodes can also have event handlers attached to them, and once an event is triggered, the event handlers get executed. Essentially, it connects web pages to scripts or programming languages.