A more thorough explanation:

A protective sweep is a quick and limited search conducted by a police officer after they have lawfully entered a premises. This search is based on a reasonable belief that it is necessary to protect the officer or others from harm.

For example, if a police officer responds to a domestic violence call and the suspect is believed to be armed and dangerous, the officer may conduct a protective sweep of the premises to ensure that there are no other individuals who may pose a threat to the officer or the victim.

Another example is if a police officer is in pursuit of a suspect who has fled into a building. The officer may conduct a protective sweep of the building to ensure that the suspect is not hiding and waiting to ambush the officer.

These examples illustrate how a protective sweep is a necessary tool for police officers to ensure their safety and the safety of others while carrying out their duties.