The Document Ready Event is to prevent or stop any jQuery code from running before the document is finished loading or the document is ready. It is good and best practice to wait for the document to be ready and fully loaded before working with it.

$(document).ready(function(){
? // jQuery methods code go here...
});

This also permits or allows you to have your JavaScript code in the head section, before the body of your document.
Here are some examples of actions that can fail if methods are run before the document is fully loaded:

1. Trying to hide an element that is not created yet
2. Trying to get the size of an image that is not loaded yet

$(function(){
 // jQuery methods go here...
});

Use the syntax you prefer. It is advisable that the document ready event is easier to understand when reading the code.