Keyword stemming is the process where search engines recognize and index variations of a keyword's root. For example, from "run," variations like "running," "runs," and "runner" are recognized. This matters because it helps ensure that your content is found when users search for related terms, not just the exact keyword you targeted. By including stemmed variations naturally in your content, you increase the chances of appearing in relevant search results. It also improves the overall relevancy of your content to user queries, enhancing your website's visibility and attracting more organic traffic.