What does (function($) {})(jQuery); mean?

Question

I am just starting out with writing jQuery plugins. I wrote three small plugins but I have been simply copying the line into all my plugins without actually knowing what it

Answer 1

Type 3, in order to work would have to look like this:

(function($){
    //Attach this new method to jQuery
    $.fn.extend({     
        //This is where you write your plugin's name
        'pluginname': function(_options) {
            // Put defaults inline, no need for another variable...
            var options =  $.extend({
                'defaults': "go here..."
            }, _options);

            //Iterate over the current set of matched elements
            return this.each(function() {

                //code to be inserted here

            });
        }
    }); 
})(jQuery);

I am unsure why someone would use extend over just directly setting the property in the jQuery prototype, it is doing the same exact thing only in more operations and more clutter.