Pop-ups are a type of online advertisement that appears suddenly on a website, often in a new window or tab. They can be used to promote products, services, or special offers, and are designed to grab the user's attention. While some pop-ups are informative, others can be intrusive and disrupt the browsing experience. Many web browsers and applications now include features to block pop-ups, as they can be annoying to users. Advertisers often use pop-ups to increase visibility and engagement, but excessive use can lead to negative perceptions of the brand or website associated with them.