When adding images within your products you have the ability to give each product a description. This description text also acts as your alt text when customers hover over your image(s) with their mouse cursor. This also comes into play with the search engines, and the overall page rank of your store.
a. It is important to have full detailed image descriptions in ever product that has images. Our best suggestion is to make each description as unique as possible.
b. This will allow for web accessibility for the blind listening to screen readers.