What is the DOM?

A reader recently wrote in asking me what the DOM was. They said they've heard it mentioned and eluded to, but aren't sure they really understand it.

We can fix that.

But the HTML you write is parsed by the browser and turned into the DOM.

View Source just shows you the HTML that makes up that page. It's probably the exact HTML that you wrote.

It might look like different code if, for example, you work in template files …

What is the DOM? is a post from CSS-Tricks