A situation is called [[Pareto optimal]] or [[Pareto efficient]] if no change could lead to improved satisfaction for some agent without some other agent losing or if there’s no scope for further Pareto improvement.
The Pareto frontier is the set of all Pareto efficient allocations, conventionally shown graphically. It also is variously known as the Pareto front or Pareto set.
Using this concept for social planning is probably a bad idea.