An alt tag is an HTML attribute applied to image tags in order to procure an alternative text for search engines. It is also knowns as "ALT Attribute" and "ALT Description".
Applying images to alt tags has a positive impact on search engine rankings.
Search engine robots cannot interpret images, therefore, ALT tags provide opportunity for readibility.
Alt tags are also beneficial for visitors on browsers that can't process images or on a screen readers' webpage.
Alt text is included in the image tag:
Product images have to be optimized for site speed and have the same keyword as the product page.
The text should be kept short and include the topic to maximize its impact.