(Copied from original User Voice forum)
"...prosets basically do what the soup group node does, it allows you to feed different selections in a procedural way to nodes such as extrude, bevel, delete and so on."
Some links:
https://vimeo.com/255782110
https://www.youtube.com/watch?v=wgroXzvUcy8&list=PLd9alCBg4-MdfihG_bbQrEG6C2W9zH_Qv