how can i tell what package a prius has?

Hi. I've being looking for my first prius. It looks like it will a 2004 or 2005. I've been doing a lot of reading and shopping. I've tried searching for information about the differances between option packages and how to figure out what package a car has. Is there a thread here that explains this? And what's the differance between a base, natl and an se?
I'll be looking at a 2004 base Monday evening. Don't know what extras it has yet as the dealer does even have it on his lot yet.
Hope someone can piont me in the right direction
Thanks

 

Thank you. I was getting frustated searching,
I guess I was making my search too complicated.
I usually use google search and ask a question just like I am talking to a person.
Your replies answered my question and helped me understand this stites search requirements better
Thank you again
BenQ