Duplicate content refers to identical or very similar content that appears on multiple web pages or websites. It can be within a single website or across different domains. Search engines like Google consider duplicate content as a potential issue because it can confuse their algorithms and affect the user experience. When search engines encounter duplicate content, they may choose to show only one version in search results, potentially impacting the visibility and rankings of the affected pages. To avoid duplicate content issues, website owners should ensure that each page offers unique and valuable information, use canonical tags when necessary, and avoid content scraping or copying from other sources.