The synod of bishops is a group of bishops who have been chosen from different regions of the world and meet together at fixed times to foster closer unity between the Roman Pontiff and bishops, to assist the Roman Pontiff with their counsel in the preservation and growth of faith and morals and in the observance and strengthening of ecclesiastical discipline, and to consider questions pertaining to the activity of the Church in the world.
Source: Code of Canon Law (Vatican.va)