POP and IMAP are mail server configurations. The easiest way to work out which is best for you is to answer this simple question; Do you access your email on more than one device?
If the answer to this is yes, then IMAP is better for you.
With IMAP email remains stored on a remote server, the greatest advantage of this is your unread email is in sync no matter what device you are on. If you read an unread email on your phone, when you begin looking at email on your computer it will appear as read. The same applies for if you move an email to a folder or delete it, the action takes place across all devices.
POP email is downloaded to a device before it is displayed, this takes up storage space and makes email more difficult to manage across multiple devices.
In most cases, IMAP is a better mail server configuration.