How does push work on ipod touch with respect to auth credentials?

I installed this instant messenger program called IM+ that keeps your accounts online even when you exit the application (you know... touch: only one app at a time) it accepts push deliveries to report you have a message.

I am kind of puzzled on how they can keep me logged in and send me a push notification that someone is messaging me. I noted the same happens for mail. If I receive a mail, even if I don't have mail open, a badge appears near the icon.

My main concern is the password. How does push work? does it mean that apple or the company 开发者_运维知识库behind IM+ stores my email and instant messenger passwords to keep me logged in and push me a notification when I have something new ?

Edit: ok... the tumbleweed is a bit too much for such a question.

Read this to understand how it works: Apple Push Notification Service