ALT text is important because it provides context to an image by describing it. It's primary use is for screen readers, so that people with visual impairments can understand what the image is trying to display. It's also used in place of an image when it can't load on the page.

From an SEO perspective, ALT text enhances the relevance of content for search engines, contributing to more accurate indexing. As search engines cannot "view" an image directly, it uses ALT text and vision algorithms to determine what the image is displaying. This increases the likelihood of the image appearing in search results, driving more traffic to the site.

Effective ALT text should be concise and descriptive, accurately reflecting the image's content and context, which in turn improves the overall user experience and accessibility of the web.