When you registered your e-mail account and provided your password, BIS is now in linked into the chain that is receiving your e-mails. When BIS gets incoming, it compresses the data and 'pushes' it to your BB, so essentially the e-mails get sent to 3 sources, your inbox, BIS, and then relayed simultaneously to your Berry.
The magic is that your BB is a passively receiving the information, unlike other devices that power up, login,search, download, logoff, and shut down, only to repeat the process at a preset interval. To boot, since the data is a compressed 'packet', vs. a stream of information, your BB requires much less power to get the job done.
Posted from my CrackBerry at wapforums.crackberry.com
