Kohana events are points in the Kohana process than methods can be hooked to.  These methods are static, and they should never be instanced.

Kohana’s helpers are for static methods where the class does not need to be instantiated in order to use the methods.  You can consider these methods as handy functions that you can use throughout your application.  Helper classes are auto loaded by the framework so there is no need to include them.  Helper files are [...]

Kohana’s libraries are for things like captcha, session, and authentication where you need a class that will be instantiated in order to use its methods.  Kohana’s Libraries are auto loaded by the framework so there is no need to include them.  You need to put the library files in the application/libraries folder.  Library class names [...]

The Kohana controller is what will control what happens between the models and the views in an application, MVC (model view controller).