The hidden fields and JS are JSF functionality. You'd be better off asking on the myfaces (unless your using the RI, in which case ask there).
IMO The best way to get some detail on Seam is to have a look through the source code.
I think you need to ask more specific questions - how does Seam work is quite general (there are already over 100 sides written in the reference manual on just that!)
You're right, I need to ask a more specific question, so I'll start with the following:
When using client-side state saving, where and how is the state saved on the client? Are all the components serialized to the client (is that what's basically in those hidden fields) or what? Does the server really store no state whatsoever about a particular client?
(When I get into really detailed stuff like the meaning of each hidden field, I'll take it to the MyFaces forum, but for now I like it here... :)
This is really a MyFaces question, so please try their forum/mailinglist/whatever.