Google has had two major series of updates recently. One has been name Panda and the other one Penguin. They both target low-quality website and intend on dropping them in the rankings and promoting higher quality websites.
The intent of the Google Panda update is to drop low-quality websites in the rankings such as websites that copy their content from original sources. The sources could be news websites, article banks or other competing websites.
So, for Panda the target is not necessarily spam sites, just low-quality websites. The first iteration of Panda or Panda 1.0 actually started on February 24, 2011, though it was called the Farmer Update back then.
The Google Penguin algorithm update started on April 24, 2012. The main target of Penguin is web spam. The sites targeted are those that violate Google’s quality guidelines. Black hat SEO tactics such as hidden text, keyword stuffing and cloaking would be targeted by Penguin.
Some of the other areas that Penguin seems to be targeting is low-quality article marketing, blog spam and overuse of exact keyword matches in links and domain names.
What had many people confused is that around April 25, 2012 both Penguin 1.0 and Panda 3.0 were rolled out leaving many webmasters and business owners scratching their heads frantically over what was happening with the rankings.