Contrary to popular opinion, Google until 2010 did not penalize web sites that have duplicated content on them, but the advances in filtering techniques mean that duplicate content will rarely feature well in SERPS. Article spinning requires "spintax". There are a number of software applications which will automatically replace words or phrases in articles. For example, the word "picture" could be replaced by the word "image" or "photo". Spintax (or spin syntax) is the list of text, sentences, or synonyms that are embedded into an article. Writers also spin their own articles, manually or automatically, allowing them to sell the same articles with slight variations to a number of clients or to use the article for multiple purposes, for example as content and also for article marketing. 
The duplication of web content may also break copyright law in many countries. If the original articles are plagiarized from other websites or if the original article was used without the copyright owner's permission, such copyright infringements may result in the writer facing a legal challenge, while writers producing multiple versions of their own original writing need not worry about such things. This ensures that a large percentage of words are different from the original article.  . In 2010 and 2011, changes to Google's search algorithm targeting content farms aim to penalize sites containing significant duplicate content. It works by rewriting existing articles, or parts of articles, and replacing elements to provide a slightly different perspective on the topic.
Article spinning is a search engine optimization technique by which blog or website owners post a unique version of relevant content on their sites. The spinning software then substitutes your synonym choices into the article to create new, unique variations of the base article. Thousands of word-for-word combinations are stored in either a text file or database thesaurus to draw from. Many article marketers believe that article spinning helps avoid the feared penalties in the Search Engine Results pages (SERP) for using duplicate content. Website owners may pay writers to perform spinning manually, rewriting all or parts of articles. Automatic rewriting can change the meaning of a sentence through the use of words with similar but subtly different meaning to the original.