Learn in the textbookMail, File, and Operations Protocols
DefinitionPOP is the protocol a mail client uses to retrieve mail addressed to you from the mail server and download it to the device.
ExplanationThe widely used version is POP3. By default it downloads mail to the device, manages it there, and deletes the original on the server, though a setting can keep a copy.
AnalogyIt is like collecting everything in your post office box and taking it home. Once home, you sort it there.
Memory hookIt stands for Post Office Protocol, literally "post office." Think of it as going to the post office to pick up the mail held for you.