A most used function of Mootools is the $ function. It’s a bit confusing with JQuery and that’s why conflicts with JQuery if used on the same page. $ selects a dom element from the document by its id. The syntax is $(‘element_id’). There is another pretty good function that I like is $$ function. It selects elements by class name or tag etc. More on this functions are available in Mootools documentation.
Mootools Request feature is another great thing to have. This AJAX calling function is capable of sending AJAX request either in GET or POST method.
These are the basic functions one may need to develop a regular web application. There are also other common helper functions for Array, String, Number, Cookie etc. For detail idea about Mootools, it is suggested to visit Mootools Documentation at http://docs.mootools.net/
For Mootools, this onLoad wrapping syntax is like this:
//Your Code Here