✔Post Office Protocol (POP) means that all of your emails is downloaded from your Internet Service Provider to your own personal computer and (usually) deleted from the server. If you created folders in your email program, those folders are only accessible on your own personal computer.
✔POP is an application layer protocol in the OSI model that provides end-users the ability to fetch and receive email.
POP=Post Office Protocol
FTP=File Transfer Protocol
SMTP=Simple Mail Transfer Protocol
TCP=Transmission Control Protocol