What is Ihtmldocument2?

Question

When it’s used, how it’s used, I can’t find anything to explain it to me?

Code example:

WebBrowser wb = new WebBrowser();
wb.Navigate(new Uri(location, UriKind.Absolute));
IHTMLDocument2 myDoc = new HTMLDocumentClass();
myDoc.write(new object[] { wb.DocumentText});
myDoc.close();