Adults
It's a holiday where you boil eggs and dye/decorate them, set them out for an anthropomorphic rabbit, and wait for it to collect them. Then the giant rabbit, appeased at your participation, hides them in a predetermined area. Sometimes the rabbit will add extra eggs (usually plastic filled with candies, treats, and money), and, if you've been good enough to make Santa's Nice List during Christmas, it'll leave a basket full of treats (toys, games, more candy, so forth). Usually inside your place of dwelling.