A more thorough explanation:

Praefectus vigilum (pronounced pri-fek-tus vi-jil-um) is a Latin term that means "prefect of the watch." In Roman law, this was an officer who was responsible for maintaining public safety and preventing fires. The praefectus vigilum was subordinate to the praefectus urbi, who was the chief magistrate of Rome.

The praefectus vigilum had the power to punish people who broke the law and disrupted public peace. They were responsible for patrolling the streets, putting out fires, and responding to emergencies.

One example of the praefectus vigilum's duties was to ensure that people didn't light fires in the streets. This was important because Rome was a densely populated city, and fires could quickly spread and cause widespread damage. The praefectus vigilum would patrol the streets at night, looking for any signs of fire or smoke.

Another example of the praefectus vigilum's duties was to maintain public order. They would arrest people who were causing disturbances or breaking the law. For example, if someone was caught stealing, the praefectus vigilum would arrest them and bring them to trial.

Overall, the praefectus vigilum played an important role in maintaining public safety and order in ancient Rome. They were responsible for preventing fires, responding to emergencies, and enforcing the law.