Google Penguin is the code name given to a major update to the Google Algorithm, that was released in April 2012. The update was focussed on reducing the ranking of websites that use black-hat SEO techniques to improve their ranking. These black hat techniques are in direct violation of the Google Webmaster Guidelines and consequently the changes were generally considered to be a positive move to eliminate untrustworthy sites.

The main aspects of the Google Penguin update are the reduction of:

1. keyword stuffing;
2. cloaking, unexpected redirects, doorway pages;
3. participating in link schemes;
4. deliberate creation of duplicate content;
5. content scraping

The update is intended to reduce the amount of web-spam and is likely to lead to a better web browsing experience.

"Google Penguin is all about ensuring that the Google Webmaster Guidelines are adhered to"