Web Notifications are messages that websites can send to users even when they are not actively browsing the site. These notifications appear on the user's device, similar to alerts from mobile apps, and can inform users about updates, messages, or reminders. Users must grant permission for a website to send these notifications. Web Notifications enhance user engagement by providing timely information without requiring users to check the website constantly. They can be customized to include text, images, and action buttons, allowing users to interact directly from the notification. This feature is supported by most modern web browsers.