It shows what happens when one searches for the username "666" on YouTube and then refreshes the page a few times. After refreshing it repeatedly, YouTube becomes darker and darker before taking him to a channel by the name of 666. The channel had 666 subscribers and views. He clicked on one of the videos on the channel, and right off the bat it was gory. At the end of it, it pauses to give the illusion of a bloody hand on your screen.
The video was made by PiroPito himself.