An IMAP email account is different from a POP3 account in that messages are stored on the server at all times instead of being downloaded to your computer. This can be useful if you share the same email address among several people, or if you travel a lot and wish to keep all of your emails on the server at all times. The disadvantage of such an approach is that you will use more disk space and the service could be a bit slower if your account has a lot of messages.
To use an IMAP account with an email client such as Outlook or Apple Mail, you need to add an email account and choose the IMAP protocol, specifying:
IMAP Server: mail.yourdomain.com (replace yourdomain.com by your domain name).
Username: your full email address.
Password: the password that you chose upon creating the email account in your cPanel.