Panda is a Google algorithm update from 2011 that aims to improve search quality by favoring websites with high-quality, original content over low-quality sites. It analyzes factors like design, trustworthiness, speed and content quality. Sites can be impacted if they have low-quality pages like tag pages, duplicate content, or pages created just for keywords rather than user intent. The document provides advice on how sites can improve by identifying and removing low-quality pages, adding fresh original content, and building more internal and external links to strong pages. It warns that sites still risk future Panda updates if they do not proactively address quality issues.