The POP3 protocol is designed to download mail from the server to an email client, or to another server. Emails are downloaded directly to the user's local disk and are then deleted from the server
(unless the user sets it otherwise). The advantage of this protocol is that you can work with your emails offline, without an internet connection.
The IMAP protocol allows not only downloading emails from the server to a local disk, but also managing the account directly on the server. IMAP is worth using if you access your mailbox from various computers or mobile devices. If you make any change to your emails (for example, read unread mail), you will see that change when connecting from another computer as well. IMAP offers a number of other advantages, such as the ability for several users to access a mailbox at the same time, working with folders directly on the server, the certainty of emails being “backed up” on a remote server (in case of a problem with your computer), the ability to display message headers without having to download the message texts (for example, when accessing from a mobile phone you save data by not downloading emails you do not need to see), and more.