Duplicate content is a problem for SEO. It confuses search engines and requires them to spend more resources locating the original. Until the search engine finds the real deal, the page will be withheld from rankings, which can have serious implications. Fortunately, there's an easy solution.
Before going any deeper, keep in mind that duplicate content isn't the same as plagiarism in this context. Plagiarism takes parts of an article or post and claims them as its own, whether or not you mean it. Duplicate content, on the other hand, creates multiple pages of the same article or post, normally due to poor URL structure.
According to Moz, there are three main types of duplicate content. Click tracking, widely used in PPC, helps analytics organize webpage traffic data. Printer-friendly pages are those that can be printed in a more streamlined format. Session IDs track unique visitors by assigning a specific number, helping discerning hits from visits.
While these assets are helpful in SEO, they often create confusion for the crawlers. According to Moz, the best way to handle duplicate content is to redirect duplicate pages to the original, called a 301 redirect. It tells the crawlers that the redirected page is the new primary and will proceed to redirect traffic there. The URL assets from the duplicate pages will be carried over.