The alt text tag helps search engine bots to make sense of a given image. Alt text tags are visible to both visitors and engine bots. Providing information about an image while creating relevant tags helps engine bots to perceive the image more accurately. For example, the "chair" alt text tag will not be sufficient for an image containing a black leather chair. It would be more appropriate if the alt text tag was "black leather chair", in which case the details of the relevant image could be conveyed more accurately. Alt text tags are also very important for visually impaired visitors who use screen readers because these tags enable such users to figure out what an image contains.