What is the meaning of a discretionary death sentence?

Punishments in Islamic Sharia are divided into three types: Qisas (retaliation in kind), Hudud (fixed punishments), and Ta'zir (discretionary punishments). Ta'zir is a disciplinary measure for sins that do not have a prescribed Hudud punishment, and the general principle is that it should not reach the level of killing. However, killing is permissible as a Ta'zir punishment in certain crimes, under specific conditions, as an exception to this principle; this is for the realization of public interest, or if the corruption of the offender cannot be eliminated except by killing them. Among these crimes are the killing of a Muslim spy, one who propagates innovations (bid'ah) that contradict the Qur'an and Sunnah, and repeated crimes whose nature necessitates killing.