URI routing question

[eluser]Assim[/eluser]

Code:

$route['product/(:num)'] = "catalog/product_lookup_by_id/$1";

I didn't understand that from the manual, what is going to be the value of the variable $1?

[eluser]Assim[/eluser]
Let's say I have something as "page" (class) in the first segment, "view" (function) in the second, and the page ID (parameter) in the third segment. But I wanted to change that so that I can remove view (function) using the URI routing, so that it will be something like:
http://www.example.com/index.php/page/id (where id is the page id) instead of http://www.example.com/index.php/page/view/id

What line should I add to the routes.php file?