As the major search engine, Google has many different facets of its complex algorithm to decide which webpages should be shown for a query and the order in which they should be displayed. Their is a core search algorithm but Google also has individual algorithms for specific purposes.
There is an algorithm called the ‘page layout algorithm’ and the ‘Panda’ algorithm. Both of these deal with the complexities of page and website quality. Google wants to make sure only quality information is served to its searchers otherwise they would quickly diminish in terms of popularity. So website and webpage quality is an important factor and one that deals with many different elements.
One element of website quality is the content on the page. Specifically Google wants to know if you are the originating author or whether the content was written by somebody else. It is not really recommended to use other peoples content and Google will not rank two separate page urls that have the same content on them. Google will most likely reward the originating author so that the duplicate content will not be placed high in their search engine.
No this doesn’t mean that you can’t use duplicate content on your website. You only want to avoid having it on a page that you want to be shown for a keyword in the search engines. If the content isn’t to be ranked then duplicate content may not matter as much. Using duplicate or partially duplicate content can be useful for other strategies. Curated content is one such strategy that uses other peoples content. The trick is to come up with your own enticing headlines and also add your own opinions in the way of comments. If you do use this strategy make sure you always cite the originating author and source.
So to recap, don’t get to hung up about duplicate content. Just be sure that you don’t use it as a piece of content you don’t want to rank in Google. Use it for other purposes and if you do be sure to cite the originating author.