The nofollow attribute is an HTML tag value used within hyperlinks to instruct search engines not to pass ranking credit, or "link juice," to the linked page. By adding rel="nofollow" to a link, website owners can prevent search engines from associating their site with the destination URL, which is commonly used for untrusted, user-generated, or paid links. While users can still click and follow the link as usual, search engines typically do not consider nofollow links when determining search rankings.