Help for htacces or routing

Hi Paul and thank you one more time for your help
I was reading with attention the route config file guide and I have to say that it was a misunderstanding in my topic.

So route is:

Code:

$route['brands'] = 'categories';

This example above says that if routing class found in the url the word 'brands', that link is remapped to a controller categories.
So 'categories' is something that already have to exist. This is a remapped.

In fact, putting:

Code:

$route['brands'] = 'categories';

is correct, but putting

Code:

$route['brands'] = 'my_word_is_not_a_controller_or_function';

I receive a warning...

I don't want a remapped action, I want a rewrite action.
In my idea, I'd like that the normal class/method/param were mapped correctly but with other words, beacuse of the slugs are depending by the user that introduces data...

I hope I explain good myself...

Please tell me if my thought is correct...

Giorgio