If you're more of a graphic desginer, then you'd need to only understand css mark up and html, for the most part.
If you're more interested in the back end, You'd need to have working knowledge of php and an understanding of working with sessions and databases.
i know this kinda tough, so no worries if you cant help. just make sure be there to experience it.
![Cheeky Tounge :p](./images/smilies/TR_tounge.gif)