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In web design, a hero image is a large web banner image, prominently placed on a web page, generally in the front and center. The hero image is often the first visual a visitor encounters on the site; it presents an overview of the site's most important content. A hero image often consists of image and text, and can be static or dynamic (e.g. a rotating list of images and/or topics).
The content presented varies with the purpose of the site: it can be relevant news about the site, specific site-links, or - in the case of e-commerce - the best-selling or strategically placed products or services.
Video Hero image
References
Source of the article : Wikipedia