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. A Roman Catholic bishop appointed an auxiliary bishop, a papal diplomat, or an official of the Roman Curia is appointed to a titular see.