POP3 (Post Office Protocol version 3), along with IMAP, is one of the most widely used email transfer methods. POP3 simply copies every message in your email account to your local computer. No information is sent back to your email account about message replies, forwarding, etc. If you use multiple computers to check your email, it is advised that you use IMAP instead of POP3.
Note: Email storage counts against your total Disk Space limits.