Bänner
From Joomla! Documentation
This is an article about web banners. To learn about the Joomla! banner component, see our Banner help screen.
Web banners (also called banner ads) are a common form of advertising on the web. They are called this because, like real-world banners, they are usually in a high-aspect-ratio shape (narrow and tall, or short and wide). They are usually placed on websites with high-quality content and link back to the advertisers' websites. Sometimes they are simple images combined with some HTML and JavaScript. Increasingly often they also use multimedia objects to play animations and sounds, employing technologies like Flash, Shockwave or Java, to attract attention.
Impressions refer to the number of times the banner has been displayed, while click-throughs refer to the number of times that users have clicked on the displayed banners. The original content provider on whose page the banner was displayed receives a small payment for each impression and a more substantial payment for each click-through, which will often be used to pay for the costs of providing the content to the users.
If banners are too attention-grabbing, users often get annoyed with them and employ an ad-blocker, which prevents the display of banners.
More info on banners is available on Wikipedia.