What's "headless" programming?

I'm popping the hood on PhantomJS (http://phantomjs.org/). Great little program, but it involves some things that have me scratching my head in that I'm not very familiar with command line programming, although I'm resolved to become familiar with it.

Here's what I understand at this point...please tell me if I'm right:

PhantomJS - is defined as "...a headless WebKit scriptable with a JavaScript API."

"Headless... " - "A headless browser is a web browser without a graphical user interface. In other words it is a browser, a piece of software, that access web pages but doesn't show them to any human being. They're actually used to provide the content of web pages to other programs."

So, part of what constitutes the way in which PhantomJS accomplishes it's "mission" is to take the content of the page it's interacting with and route it through a "headless" dynamic that then presents it to the code that will manipulate it.

Yes?

Webkit scriptable - this is a web engine that combines content and formatting for electronic display.

This is another element that qualifies PhantomJS as being far more verbose than just a typical line of Javascript. With PhantomJS, you're actually popping the hood on the machinery that presents your content to your end user. If regular HTML and Javascript could be thought of as the parlor, you're now in the living room.

Correct?

Javascript API - Application Programming Interface. So, you're using Javascript to communicate the commands that are manipulating your content to the Webkit engine.

Is that right?

I will have some more questions, but I want to start with these in that they strike me as foundational.

What do you think?