Penguin is actually a Google algorithm update that was first released in 2012 to help Google keep it real with its search results. This algorithm detects the unnatural, spam or low quality links in a website. As a result, a website that may have an article that is over-optimizing keywords, has spamming external and internal links will be filtered by Penguin and Google downgrades the rankings of such websites.
If you’re still confused, it helps by understanding what a Google penalty actually is. When your site gets a Google penalty, it either affects few of your pages (as is the case with manual penalties) or it affects your whole site (when you get hit by an algorithmic penalty). In either case, your search engine results suffer. Your keywords do not get a search engine ranking causing your site to drop out of search results. You lose out on your target audience as a result of Google penalties. Google penalizes your site when it detects too many spam and bad links on your website or when the content is low quality. Mobile friendliness is a recent criterion added to Google penalties. Too many keywords or misplaced anchor text also can be the cause of a Google penalty.
Google will either hit you with a manual penalty and then notifying you via search console or your site will lose out on traffic and ranking due to an algorithmic penalty.
Thus, it can be now understood that Penguin itself is not a Google penalty but an algorithmic update that still helps Google deliver the best results for each search query.