What does 'Web Notification' mean?

Notifications transmitted to a user's desktop or mobile web browser are web notifications. Depending on the operating system, these are alert-style notifications that appear in the top or bottom right-hand corner of a desktop screen or on a mobile device like app push notifications. They are displayed on a user's desktop or mobile screen whenever their browser is open, regardless of whether they visit the website. They are a form of permission-based marketing. Users must opt in to get online notifications before they can receive them. The user's web browser generates the opt-in prompt.