What is a separate window that opens a browser without user interaction?

A popup is a type of window that appears over the existing web page content, often without any direct action from the user, like clicking a button or link. This feature is commonly used for advertisements, subscription forms, or additional information that complements the content of the webpage. Popups can be triggered by a variety of factors, such as a specific time delay after a page loads or a user navigating to a particular section of the site. This is why popups are often associated with unsolicited content, as they can appear abruptly without user expectation.

In contrast, a modal typically requires user interaction to proceed, such as closing it or taking action within the modal itself. Dropdowns generally refer to a type of menu that expands when clicked and requires some user interaction to reveal options. Sidebars are generally persistent elements within a webpage layout that can contain navigational or supplemental information but do not pop up unexpectedly like a popup does.