Why we use? http://localhost/codeigniter/index.php/blog

[eluser]Unknown[/eluser]
Why we use http://localhost/codeigniter/index.php/blog? why?

Can I change it? if yes, how?

I want to use http://localhost/codeigniter/index.php/test

but when i use it. error occur. url not found...

Please help and guide me

Regard
Ravian