Complex sentence: Therefore a priest appointed not to head a diocese as its diocesan bishop, but to be an auxiliary bishop, a papal diplomat, or an official of the Roman Curia, is appointed to a titular see.
Split into simpler sentences: Therefore a priest appointed not to head a diocese as its diocesan bishop, is a titular bishop. Roman Catholic bishops appointed an auxiliary bishop, a papal diplomat, or an official of the Roman Curia, is appointed to a titular see.