It's a PDF, a ZIP, and an HTML page:
  If you drop it on itself in a browser,
  it can give you a PDF viewer, a video
  and a PNG explaining the whole file structure.
  All these files have the same MD5.

The explanation for how the MD5 trick is achieved is in the PDF, starting on page 21.

Edit: whoops, probably more relevant is this earlier issue, which has the MD5 printed on the cover. https://github.com/angea/pocorgtfo/blob/master/contents/issu... The relevant article in that issue starts on page 46.

https://news.ycombinator.com/item?id=13823704