Slatin and ALT

"Images should include  equivalent alternative text  (alt text) in the markup/code.

If alt text isn't provided for images, the image information is inaccessible, for example, to people who cannot see and use a screen reader that reads aloud the information on a page, including the alt text for the visual image.

When equivalent alt text is provided, the information is available to people who are blind, as well as to people who turn off images (for example, in areas with expensive or low bandwidth). It's also available to technologies that cannot see images, such as search engines." (1)

For more on Slatin see here

Sources

(1) https://www.w3.org/WAI/fundamentals/accessibility-intro/#examples