Ranking signals are the various factors and criteria that search engines use to determine the position of a webpage in their search results. These signals include both on-page factors, such as the relevance and quality of the content, as well as off-page factors, such as the number and quality of backlinks pointing to the webpage. Search engines analyze these signals to assess the overall authority, relevance, and trustworthiness of a webpage, ultimately influencing its ranking in search engine results pages (SERPs).