Google Penguin is a search algorithm to reduce the ranking of websites that violate Google’s Webmaster Guidelines using black hat SEO to artificially increase a page’s search ranking. Although Penguin also evaluates on page factors, it most famously targeted link schemes. Unlike Google Panda, Penguin is applied to individual pages.
Originally, Penguin would run periodically and apply/remove penalties only once in a while. With the release of Penguin 4.0, it has been incorporated into Google‘s core algorithm and runs in real time.