User blog comment:Lord Loss/Monster Hunter Portable 3rd on the PS3/@comment-86.134.241.117-20110523145854/@comment-969093-20110523212315

Adhoc Party works like an infrastructure mode (a real one, like the one they promised back when developing unite but never got around to making) and allows people to connect to other players around the globe via the same "Adhoc" mode you'd use to play with friends nearby.

You could see it like playing online via Wifi.