This feature would allow world creators to set certain worlds available to their freinds without having the world public.
The three new world options are
Owners friends: allows friends of world creator to make a new instance of the world but only friends of the owner can join. Instance types; invite, invite+, friends
Friends private: allows friends of owner to make an instance of the world that is either invite or friends but other joining users do not have to be friends with owner. Instance types; invite, friends
Friends open: allows friends of owner to create an instance with no restrictions( sudo public) instance types; invite, invite+, friends, friends+