Jquery,fn,extend and Jquery.extend

1 to think of jquery as a class, Jquery.extend () is a static method that extends the class, that is, the extended global function, which is only related to the class itself, regardless of the instantiation object of the specific jquery class.

For example: $.each ();

2 jquery.fn.extend extension is a method of the jquery prototype object that can be used only by instance objects of the jquery class.

For example: $ (' #aa '). Eat ();

Jquery,fn,extend and Jquery.extend