What's the purpose of creating jQuery code inside this elements like this

Question

    (function ($) {
       ...
    } ) (jQuery);

Answer 1

To avoid conflicts with other javascript libraries that also use $.

This method, however, allows you to use $ in that function at your will, no need to use jQuery there.

That pattern is also important when writing jquery plugins.

Answer 2

It creates a function, with $ as an argument, and immediately runs that function with jQuery as the argument. Effectively this will ensure that $ points to jQuery inside your code, even if jQuery.noConflict() is used.