The term popup is associated with the online advertisement campaign and is refers to popup advertisements. These kinds of ads are popularly used by the websites and are generally a part of their advertisement campaign. The main purpose of the popup ads is to get more traffic to the website and diverts people to the advertised site.
The popup windows are considered to be annoying by the user. In this case the user can use a popup blocker that can block such advertising windows and work on their active window without any disturbance.
If you need to get good web traffic to your site then you can contact a company that deals with online media and can help you get popup advertisement for your ad campaign.