IMAP and POP are two popular internet email protocols (methods) which enable you to retrieve mail from an e-mail account using software on your local computer such as Microsoft Outlook or Mozilla Thunderbird.
IMAP stands for Internet Message Access Protocol.
The IMAP protocol allows you to read your mail while it is still on the mail server. This allows you to keep your mail in a central location accessible from any IMAP-configured computer.
POP stands for Post Office Protocol.
POP is different in that it downloads your mail to the computer, removing it entirely from the server. This is handy in that you can always read your downloaded mail on the PC, even if the network goes down. However, you won’t be able to read your existing mail if you’re at a different computer.