GIFs are another form of banners which are animated or still images that include images and content and bear the .gif extension. Animated GIFs contain various images (frames) that are shown one after another and thus creating the sense of motion. Gifs are popular but nor as popular as flash banners. Sanchit Bhatnagar in this post tells us why flash banners make more sense than gif banners.
In order to improve the consumer experience, flash banners are frequently interactive. It means that they respond in accord with the user’s actions. The most frequent features of an interactive banner is the rollover buttons, checkboxes, in-banner navigation systems, sound on/off buttons, play-pause buttons, close buttons and so on. Also interactive banners are often flexible and/or retractable, which means they can alter their size depending on user action.
All three versions of banner ads have their own merits and demerits; it is up to the size of the business and the kind of product you want to promote which decides on which type works the best.