Catholic Social Teaching is the part of Catholic teaching that addresses matters of social, economic and ecological justice in the world. It is mainly concerned with inter-group or social relationships rather than interpersonal relationships. Like other parts of Church teaching, it is grounded in Scripture, tradition, reason and experience. It develops through time by placing these sources in dialogue with the signs of the times. Catholic Social Teaching operates at both the international and the local level and it has three elements: principles for reflection, criteria for judgement and guidelines for action. It is usually communicated through formal teaching documents like encyclicals by Popes and pastoral letters by Bishops.