Why use $ (dollar sign) in the name of javascript variables? [duplicate]

Possible Duplicates:
Why would a javascript variable start with a dollar sign?
JQuery : What is the difference between “var test” and “var $test”

What is the difference between this two ways of initializing variables?

var $val = 'something'

     OR

var val = 'something'

as I see they are the same thing.

Maybe in this case $ is only the part of name in variable? (it will become a meaningless question in that case:/)

Thanks

The $ in the variable name is only part of the name, but the convention is to use it to start variable names when the variable represents a jQuery object.

var $myHeaderDiv = $('#header');
var myHeaderDiv = document.getElementById('header');

Now later in your code, you know the $myHeaderDiv is already a jQuery object, so you can call jQuery functions:

$myHeaderDiv.fade();

To get from the DOM-variable to the jQuery variable:

var $myHeaderDiv = jQuery(myHeaderDiv); //assign to another variable
jQuery(myHeaderDiv).fade(); //use directly

//or, as the $ is aliased to the jQuery object if you don't specify otherwise:
var $myHeaderDiv = jQuery(myHeaderDiv); //assign
$(myHeaderDiv).fade(); //use

To get from the jQuery variable to the DOM-variable.

var myHeaderDiv = $myHeaderDiv.get(0);

You are correct. $ is a part of the name of the variable.
This is not perl or PHP :)