Basic index($variable) question for creating a site like www.mysite.com/username

[eluser]AlanW[/eluser]
[quote author="siptik" date="1352754412"]set route $route['(:any)'] = 'main/index/$1'[/quote]

Is this in addition to the routes I already have?


$route['default_controller'] = "main";
$route['404_override'] = '';