If you were on YouTube in the late 2000, there's a good chance that you watced a YTP at some point. I could explain what these are for those who don't know, but I think that the explanation made by prolific pooper CS188 in this video is better than anything I could write.
The thing I love most about YTPs is all of the different ways that people utilize the core concept of taking pieces of media and turning them into whatever the pooper wants to make. The end result could be somethhing like the absurd and often sexual humour of CS188 videos, the clever wordplay of DaThings videos, the political satire of many of Very Tall Bart's videos, or beautiful music made by YTPMV creators like Cake and Blizzy Mez. There truly is a staggering amount of varitey in YouTube Poops.