A question of using dollar sign...

I do'nt very clear about the using of dollar sign.

For example:

this._button$delegates =
{
click : Function.createDelegate(this, this._button_onclick)
}
(From AJAX Control toolkit)

or

Namespace.$create_AnimatedUpdatePanelOptions = function nStuff_AnimatedUpdatePanelOptions() { return {}; }
(From Nikhil's sample)

or

$get(DomElementName)
(From AJAX document, I got the meaning of this one.)

Is there any kind person to tell me the difference between those different using of dollar sign?
Thank you very much!

This is done basically for debugging support. You can read the full details inhttp://weblogs.asp.net/bleroy/archive/2007/03/15/what-are-these-foo-bar-baz-functions-in-the-microsoft-ajax-library-files.aspx

The post will be very useful!
Thanks!