Search engines generally have problems in understanding of multimedia content such as videos, photos or music files. You are here in part to the surrounding text and rely on the other to the use of the alt attribute . This attribute describes the content to be displayed and is required for example by screen readers.

Furthermore, carrying filename of the image in information retrieval. The optimization of these factors influenced definitely position a graphic in the Google image search and contributes according to Mario Fischer (Website Boosting 2.0, p 325) also also contribute to a better ranking that page that displays this image (if it fits thematically)