Duplicate content refers to blocks of text or entire web pages that appear in more than one location on the internet, either within the same website or across different domains. This repetition can be exact or closely similar, and it often occurs unintentionally due to technical issues, such as URL variations, printer-friendly pages, or content syndication. Search engines may struggle to determine which version to index or rank, potentially impacting a site's visibility in search results. To avoid negative effects on SEO, it is important to identify and resolve duplicate content issues through proper site structure, canonical tags, and consistent internal linking.