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Sean,
You can learn more using the Search function at the top of the screen. Also search for "direct push" on google.

As designed, "direct push" email involves syncing your device with a Microsoft Exchange server. The server and the device maintain a continuous (but mostly dormant) data connection over the cell network, and the server sends new emails to the device as they are received.
You don't get direct push with a POP account (although you can simulate it with some 3rd party software). Instead, you get your email in the traditional "pull" method, where your device checks the server mailbox and downloads all the mail that's in it. You can easily automate this by setting up the email account(s) on your device to check for new mail at regular intervals.