Google has multiple named parts of the algorithm that influence search rankings. Google Panda is part of the algo that is specific to the quality of content, Penguin is specific to the quality of links, and Hummingbird is Google’s part of the algo for handling conversational search queries accurately.
Google Panda takes the quality of a site’s content into account when ranking sites in the search results. For sites that have lower quality content, they would likely find themselves negatively impacted by Panda. As a result, this causes higher quality content to surface higher in the search results, meaning higher quality content is often rewarded with higher rankings, while low-quality content drops.
When Panda originally launched, many saw it as a way for Google to target content farms specifically, which were becoming a major problem in the search results with their extremely low-quality content that tended to rank due to sheer volume. These sites were publishing a fantastic amount of low-quality content very quickly on topics with very little knowledge or research, and it was very obvious to a searcher who landed on one of those pages.