CodeIgniter are designed to be search-engine and human friendly. But you can modify as per your requirement.
The segments in the URL, in following with the Model-View-Controller approach, usually represent:
example.com/class/function/input_id
1. The first segment represents the controller class that should be invoked.
2. The second segment represents the class function, or method, that should be called.
3. And any additional segments, represent the input_id and any variables (GET) that will be passed to the controller.