session_start questions.

Questions, Questions,.... Questions. Where do I start in understanding how this function works. Ive read the document multiple times, and I am having a bit of trouble figuring out how this function works. I know that you can take session data and hold it somewhere for a user and use that data throughout php web pages. I am wandering, where is this data held and how to do you reference it ? Is their a more detailed explanantion of session's ? If their is not, once I get this, I will write one for people like me. You know, .... "Sessions for Dummies" ;o) Never the less, how do you set a session name for a specific user and hold that data for processing? Is this magic from somewhere or do you specifically name a session for every user ? What about security implications ? I will be running all my forms through secured protocol so hopefully their wont be any hijacking going on... Sorry for being a pain.