input tags from an HTML
document. Such objects are part of a structure called the Document Object
Model (DOM). Every tag in the document is represented by an object in this model
and can be looked up and interacted with.
HTML documents have a hierarchical structure. Each element (tag) except the top
<html> element is contained in another element, called its
parent. This element can in turn contain child
elements. You can visualize this as a kind of family tree. If we have a simple document like