Google's Penguin algorithm was first released on April 24, 2012 and it's role is to identify and filter out spammy web pages from the search results. The algorithm targets websites employing various techniques to artificially raise their rank. Two of the main targeted techniques are keyword stuffing and link schemes. Penguin was updated four times until it was incorporated into Google's core algorithm in Sept 2016. At that time Google announced that being part of the core algorithm means that websites would be assessed by Penguin in real time. Previously, websites that were penalized would have to wait until the next Penguin update to be reassessed.
The history of the Google Penguin update