It's a Immediately Invoked Function Expression, which is a is a design pattern that invokes a self executing anonymous function. There are two parts to this design pattern. First is the JavaScript (function () { Here what is happening is the creating an anonymous function that is scoped to just that function. the second part is the () at the end of the function block. This creates an immediately executing function expression, and the JavaScript interpreter will directly invoke the function. Here is an example:

(function () { 
    var aName = "Barry";
})();
// Variable name is not accessible from the outside scope
aName // throws "Uncaught ReferenceError: aName is not defined"