Confused about libraries vs models

[eluser]Buso[/eluser]
Suddenly I found myself writting library methods like this one:

Code:

public function some_func() {
  
  $this->CI->load->model('some_m');

  $this->CI->some_m->some_func(); // this is the same name used for the library method

}

So I'm not sure anymore about when I should use libraries instead of models.

It was very clear in the beginning, when I used to think that models should only contain database related code. But now that I use tiny controllers and big models/libraries, the only difference I can see is that models can do $this->db, and libraries don't. Maybe models are only for CRUD, and libraries are something like 'subcontrollers' (meaning that they take some kind of decisions) ?

Please enlighten me.