basic of basic

1) $() function is actually a factory for jQuery object. It is the object encapsulates zero or more DOM dlements.
2) .addClass() and .removeClass()
They are fairly self-explanatory.
Its only parameter is the name of the class to add or remove.
Here are two samples.

Sample 1.

$(document).ready(function() {
It is the function to add class 'emphasized' on the class 'poem'.
Sample 2.
<div class="scode">$(document).ready(function() {

This sample try to find the span which contains “language”, and add a class ’emphasized’ on these span.