new to everything

I have not heard of Grocery CRUD, but it sounds like it's a third-party library. CRUD stands for CReate, Update, and Delete. It's the basic operations of putting data into a database. It might be better to just learn a little Codeigniter first, without any additional extras.

Like whiteatom says, your URL might look like this:
http://mysite.com/my_codeigniter/cars/show_specs/42

When you try to go to that URL, Codeigniter will interpret that as "look for the file Cars.php in the controllers folder, then execute the show_specs() function in that file, and give it the value of 42 (which is probably the database ID for a particular car)."

If you're new to programming and PHP as well, check out these tutorials.
http://www.w3schools.com/php/default.asp
http://www.webmonkey.com/2010/02/php_tut...beginners/
http://php.net/manual/en/tutorial.php

Hey, don't work without a PHP debugger. Several free IDEs have this features built in. Two are NetBeans and CodeLobster. Without a debugger, it's like you're driving with a blindfold on -- you are going to crash!