I state that are in the course of learning do jQuery ...

There are thousands of tutorials to write functions in a thousand different ways in file .js external... 

Someone can give me a hand?

1. // Do something when the document it's ready (at the end) ...Correct?
2. jQuery(document).ready(function(){
3.       alert(' I am ready ');
4. });

1. // The document learn the function and when it is called do something ... Correct?
2. function hello() {
3.       alert(' hello ');
4. }