Google Panda is an algorithm update created by Google that is released in February 23, 2011. This update upgrades the sites that people like and downgrades the sites that people dislike. The evaluation is based on design and user's experience, the overall quality of content and the usage metrics. Google Panda favors those sites that have good design, those that have easy navigation, the contents are useful and is shared by many people and most importantly, those sites that receives longer visits from various users. It downgrades those sites that have contents that are poorly written and duplicated.
Google Penguin is also an algorithm update released by Google in April 24, 2012. Its main goal is to protect the search engine from black-hat techniques in SEO. The Penguin penalizes those websites that use keyword stuffing, cloaking, link farming and duplicating contents to rank higher in search engine.