jQuery newbie: what does jQuery(function($) { … }) means?

Question

I know in jQuery, $(callback) is the same as jQuery(callback) which has the same effect as $(document).ready().

How about

Answer 1

• $(function()) is a syntax error.
• $() creates an empty jQuery object.
• $(document).ready(function() { ... }) executes the given function when the DOM is ready
• $(function() { ... }) is a shortcut for the same thing
• jQuery(function($) { ... }) does so, too, but it also makes $ available inside the function no matter what it's set to outside.