A notification is a message or alert that is delivered to a user or recipient to inform them about a specific event, update, or piece of information. Notifications can be sent through various channels, including mobile devices, web browsers, email, or other communication platforms. They are commonly used in applications, operating systems, and communication tools to keep users informed about important updates, messages, reminders, or events. Notifications help users stay updated and aware of relevant information without actively checking for updates manually.