If I understand the difference (I'm a bit rusty on this topic), using the POP protocol means you download the email every time you look at it -- which means that all of your email goes to one computer or device. IMAP allows you to access it without forcing you to download it -- which is useful if you are reading work email away from your office computer (assuming that is where you want to keep it).

A way around this problem is to use a web interface to read your email -- just like gmail, but without its drawbacks.

Geoff