Non-Codeigniter question - form processing like PayPal's login

[eluser]taro uma[/eluser]
Hi,I was wondering if anyone knew how form processing like Paypal's login works, where there is a "Loging In...." message, then you are forwarded to your account when that is done. I don't know the term used for this, so I am having no luck finding anything about it on google. I've seen similar things in some shopping carts when checking out, like "Processing your order..." and then a little animation below it.