5 Bishops chosen from various parts of the world, in ways and manners established or to be established by the Roman pontiff, render more effective assistance to the supreme pastor of the Church in a deliberative body which will be called by the proper name of Synod of Bishops. Since it shall be acting in the name of the entire Catholic episcopate, it will at the same time show that all the bishops in hierarchical communion partake of the solicitude for the universal Church.
Source: Christus Dominus (Vatican.va)