The term ‘duplicate content’ refers to content which appears on the Internet in multiple places. ‘These places’ are defined as a location that has a unique website address (URL). In other words, if the same content is displayed at more than one web address, this is said to be duplicate content.
While not strictly a penalty, duplicate content can nonetheless impact search engine rankings. As soon as there are several pieces of, as Google terms it “appreciably similar” content, in more than one place on the Internet, it can be challenging for search engines in order to decide the version which is more applicable to a given search query.
Put another way, the issue of duplicate content is best understood from the perspective of a search engine trying to provide the best possible experience to its users. If you have a number of pages with similar content on your site, you waste the Google bot’s time. Rather than wasting crawling bandwidth on duplicate content, you want all of your unique landing pages and valuable content indexed and shown in search results.
Duplicate content also dilutes the value of your link. If someone links to your page via a URL with tracking or sorting parameters, these links are actually pointing to different URLs. This causes a dilution in link equity and prevents the correct page from ranking.