IMAP
In plain terms
A protocol for accessing email stored on a server.
Going deeper
IMAP lets email clients read and manage messages kept on the server, syncing state across devices, unlike POP3 which downloads and removes. It keeps mail server-side.
Under the hood
Server-stored mail syncs folders and read status across devices; contrasts with POP3's download model.
Examples
Email clients, multi-device sync, Gmail/Outlook access, server-side mail.
Think of it like...
Like reading your mail at the post office and leaving it there, viewable from anywhere.