Post Office Protocol - Wikipedia
https://en.wikipedia.org/wiki/Post_Office_Protocol
In computing, the Post Office Protocol (POP) is an application-layer Internet standard protocol used by e-mail clients to retrieve e-mail from a mail server. POP version 3 (POP3) is the version in common use. The Post Office Protocol provides access via an Internet Protocol (IP)...
Email Protocols - POP3, SMTP and IMAP Tutorial
https://www.siteground.com/tutorials/email/protocols-pop3-smtp-imap/
POP3 allows you to download email messages on your local computer and read them even when you are offline. Note, that when you use POP3 to connect to your email account...