Need help understanding a javascript function

I'm hoping someone can explain the following usage of JavaScript.

I have a page with a script that looks like this:

(function($){
     // code 
     // and stuff
})(jQuery);

I'm trying to understand what this code does, specifically:

1. The opening parenthesis at the start
2. The usage of the $ symbol
3. The jQuery in parentheses at the end

thanks!

This is an anonymous function.

The specific example you provide is usually used when jQuery (which uses the "$") is conflicting with another library (prototype also uses "$").

What this does is say that whenever "$" is used within the function, it is to reference the jQuery object.

Normal:

$("foo").doStuff()

Conflict avoidance:

jQuery("foo").doStuff()

Using anonymous function to avoid conflict:

(function($){
  $("foo").doStuff();
})(jQuery)