A relevance link is a link that comes from a website that is closely related to the content and topic of your own website. When another website links to yours and the content on both sites aligns well with each other, it increases the link's relevance. Relevance links are important because they signal to search engines that your website is a trusted source within a specific field, which can improve your search rankings. By obtaining relevance links, you can enhance your website's credibility and authority within your niche.