Very expensive right now.
But they are amiibo cards that function similarly to amiibo's in that they each have either a villager or an admin, like Isabell or Nook, character on them. The villager cards can then be used to get that character in your village using the kiosk in Resident Services, inviting them to camp a few times and fulfilling their requests. They are also the easiest and fastest way to kick villagers out as when a new one from the camp wants to move in you can ask someone to leave without going through the standard ways.
Any really highly sought after villager's card can be sold as well for sort of insane prices.