What is Duplicate content?

Duplicate content is the content that is already published and indexed by search engines. Duplicate contents can be checked using various online tools like Copyscape. These contents are harmful for your website and should be removed immediately to avoid search engine penalties.

Duplicate content is content that appears on the Internet in more than one place. That "one place" is defined as a location with a unique website address. so, if the same content appears at more than one web address, you've got duplicate content.