What Is Google Panda and Penguin?

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The Panda update is a filter that is designed to penalize “thin” or poor content from ranking well. Whereas Penguin is a filter that is designed to penalize websites that have bad link building techniques and keyword stuffing.
Google Panda is a major change to Google's search results ranking algorithm that was first released in February 2011. The change aimed to lower the rank of "low-quality sites" or "thin sites", in particular "content farms", and return higher-quality sites near the top of the search results.
The first thing you need to know is that Google Penguin only deals with incoming links into a website (also known as “backlinks”). In other words, it looks at which sites are linking to you, not which sites you are linking out to.