what counts as google panda?

Panda was the 2011 Google update aimed at low-quality sites: thin pages, content farms, near-duplicate articles, pages buried under ads. It hit whole sites, not single pages, which is why people remember it as brutal. There hasn't been a separate "Panda update" for years, it got folded into the core algorithm. So when someone today says a site has a Panda problem they really mean lots of weak pages dragging the whole domain's quality down. Fix is the same as back then: improve, merge or noindex the thin stuff.