With an IMAP account, your incoming email stays on our mail server until you delete it. You can read and manage your email from multiple locations. You can always see your folders, ie. In, Out, Sent and Trash, plus any new folders you create no matter which device you use to access your mail account, and you can work with your messages just as if they were on your computer.
IMAP requires nothing special in relation to POP3, and is set up in the same way in your mail program, with the same login information and servers. Note IMAP uses port 143, where as POP3 uses port 110.