What characterizes a pop-up ad?

A pop-up ad is characterized by its appearance while a web page is loading, where it typically opens in a new window or tab over the current content. This technique is often used to capture the user's attention immediately, usually promoting a product or service in a way that interrupts the browsing experience.

Pop-up ads are distinct from other forms of advertisements mentioned in the question. For instance, the option regarding advertisements only appearing in emails refers to email marketing, which operates differently from web-based pop-ups. The mention of ads shown before videos pertains more to pre-roll ads, commonly found on streaming platforms, rather than web browsing pop-ups. Finally, advertisements that are exclusively shown on social media platforms denote a specific type of digital marketing strategy that does not encompass the broader phenomenon of pop-up ads.

Overall, the key feature of pop-ups is their timing and format, which specifically targets users as they navigate web content.