In general, popup refers to any UI element that floats above a window or application surface. This may include tooltips, context menus, and modal dialog windows.

A "popup" is generally a client-side (e.g. Javascript) produced User Interface element.

It might exist within the current window/page, or it may be a completely new window.

The popup may be an alert, a confirmation interface, an advertisement, and more.

Some types of popups have become such a nuisance, that popup blockers have been a favorable tool for web users.

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