Ever visited a webpage where an image didn't load and you saw text like "image not found" instead? That replacement text is often the alt text. It serves two critical purposes: it tells visually impaired users (through screen readers) what the image shows, and it tells search engines what the image is about — since Google can't actually "see" pictures.
For example, if you're selling apples and add an image with the alt text "fresh red apple," Google now understands the image content. This means your image can rank in Google Image Search, driving additional traffic. Every image on your website should have a brief, descriptive alt text — it's one of the simplest SEO wins you can get.