Final answer:
POP3 and IMAP4 are protocols for receiving emails, with POP3 downloading and deleting emails from the server, and IMAP4 allowing access and synchronization across multiple devices.
Step-by-step explanation:
POP3 (Post Office Protocol 3) and IMAP4 (Internet Message Access Protocol 4) are protocols used for retrieving email messages from a mail server. POP3 is a simple protocol where emails are downloaded from the server to the user's computer or device, and then usually deleted from the server.
It is most useful when you have one device to check your emails on and when you need to access your emails offline. IMAP4, on the other hand, allows for more flexibility by maintaining emails on the server, which allows multiple devices to access the same emails and folders. IMAP4 is beneficial when you need to access your email from different devices or when you want your emails to be consistently synchronized across all devices.