self executing function jquery vs javascript difference

Question

What are the difference among -

First :-

(function () {

    var Book = \'hello\';

}());

Second:-

Answer 1

This is called a closure to avoid conflicts with other libraries such as mootools which are using $. This way you can ensure to use $ in that function with passing jQuery as a param.

(function ($) {
   $(function () { // Here in this block you can use '$' in place of jQuery
    .......
   });
})(jQuery); //<----passing jquery to avoid any conflict with other libraries.