Over the years I cannot count how many times I have had to explain the convoluted ways that a BlackBerry can use to connect to the internet. Everything from WAP to WAP2 to TCP/IP to BIS to BES to Wi-Fi are just not that simple to describe. Every new BlackBerry developer needs to understand this so their applications can make a reliable connection to the internet. Sadly RIM has yet to provide a comprehensive guide to those not in the BlackBerry Alliance.
From now on I have a solution. Peter Strange has posted a brilliant thread on the official BlackBerry support forums detailing how BlackBerrys connect to the internet and all the issues a developer must deal with. Its a great starting point an may solve most of your questions.
Check out his thread at this link and let me know if you found any other good development resources!