What is meant by AngularJS element?

What is meant by AngularJS element?

I am trying to learn AngularJS. I was reading the
https://github.com/angular/angular.js/wiki/Understanding-Directives : "You
do NOT have to wrap AngularJS elements in jQuery()"
What is meant by an AngularJS element? In Jquery, if I have a DOM element,
say by using document.getElementByID() and if I want to make it a jquery
element with access to all of its awesome functions, I will simply say
var domElement = document.getElementByID("elemID");
var $domElement = $(domElement); (To cache the element)
So, if in angular I dont have to wrap the DOM element as in Jquery, then
can I simply query the DOM and access it and still be able to access all
the angular methods. If so, how it is done? Is it because of the ng-app
binding? Are all DOM elements inside ng-app internally accessed by Angular
and turned to equivalent AngularJS elements?