The $ parameter in the first block is unneeded in that context.
Where you would see it is in a block like this:
(function ($) {
// stuff
})(jQuery);
In that context it would allow you to always use the $ alias even if there was a conflicting library.
Ignoring that, there is no difference. $ is just an alias for jQuery.
Both are shortcuts for $(document).ready(function(){
What BNL said and yes, they are both an alias for $(document).ready(function(){
you could also write jQuery(document).ready(function(){ :)
if you only are using jQuery then both $ and jQuery is the same, but if you are using another javascript library that uses $ as a shortcut then they wont be the same. But if its just jQuery then its just like you and @BNL have written its, its the same.
The first code snipped serves the purpose of avoiding conflicts with other JS libraries that may be using the $ symbol. Wrapping the jQuery code in this manner allows you to use $ inside without worrying about conflicts. It's a good practice e.g. if you are writing a jQuery plugin to protect against conflicts in this manner. Otherwise, normally jQuery is a synonym for $.
Also have a look here for some additional info on avoiding conflicts with other libraries: http://api.jquery.com/jQuery.noConflict/
