What is the use of URI Protocol in Config file in Codeignitor

By default as you know that the codeIgniter Url is based on url segments such as given below

http://example.com/index.php/news/local/metro/crime_is_up

The segment numbers would be this:
1.news
2.local
3.metro
4.crime_is_up

Now what if you want a querystrings not a uri segment then what will you do here the uri protocol in the
config file come into picture.

Segment url :- http://example.com/this/is/a/url/segment  
Querystring url :- http://example.com/?type=text&message=hello.

Now there are two method of using uri protocol
1. Application - wide
2. Controller Specific

a) First For Application - wide
In system/application/config.php find and modify the following two lines:

//Change from 'AUTO' to 'PATH_INFO' to allow querystrings
$config['uri_protocol'] = 'PATH_INFO';

//Change from 'FALSE' to 'TRUE' to allow querystrings
$config['enable_query_strings'] = TRUE;

b) Controller Specific - This will only affect a single controller and not your entire application

In system/application/config.php find and modify the following line:
//Change from 'AUTO' to 'PATH_INFO' to allow querystrings
$config['uri_protocol'] = 'PATH_INFO';