It seems there are some very good resources on my question - at least the basics. But there are still a few dark areas for myself.
First - What I am trying to do.
I am having users "wait" at an intermediary page while I check to see if they have submitted the correct information from another resource (ie. SMS or email) to confirm their subscription to my service. The page should asynchronously check ever couple of seconds to see if they have completed the required steps and their status has been set to '1' or 'active' in the database.
Completing the ajax request seems pretty straightforward - the timing however, I am a little thick about.
Also, what is it that I am trying to do with the information I am retrieving - great, so the user has been set to 'active' and I can retrieve that value - but then what do I use to redirect them to the final or 'thank you' page? Is it a javascript variable that should hold the value then redirect?
Sorry if this seems a little discombobulated, but this is my first try at Ajax & timed refreshes/responses.