HTML5 Document Object Model (DOM)
Every time you open your Elements tab in Chrome DevTools you are looking at the DOM. The DOM provides an organized tree structure of something called nodes (which is where Node.js gets its name). Each element is a node but so is the text and other stuff on the web page.
The top level of the DOM tree for the document is actually
Open the Chrome DevTools Console and just type
document. to see all the stuff it contains.