Advertisements, e.g., banners, text links, skyscrapers, buttons, badges, email copy, pop ups, etc.
In marketing the use of the word "creatives" while talking about banner advertising for instance, we are talking about the banners themselves. For any banner campaign other than the smallest, briefest kind, having multiple creatives is a necessity. For a banner campaign of 200,000 total impressions, at least 3-6 banners should be on hand. A good ratio for this would be: at least 1 banner creative for every 50,000 - 75,000 page impressions. In this way, we can track all of the banners, and we can rotate out the ones whose performance begins to slip. (Those banners can often be used again in a new campaign, with often good results.)