What is a pop-up?

an advertizement, how companies make money ... some pop ups have viruses embedded so you should download a free popup blocker from google A pop-up is a small browser window that appears ("pops up") when you visit certain webpages. Usually they contain advertising and are widely regarded as annoying. Web Browsers like internet Explorer and Firefox contain built-in pop-up blockers that try to prevent pop-ups from appearing and free software such as the google Toolbar also have pop-up blocking features.