Final answer:
The FBI is part of the Department of Justice, which is tasked with enforcing laws and ensuring public safety. Other departments, like the Department of Homeland Security, handle specific domestic security functions.
Step-by-step explanation:
Law enforcement agencies such as the FBI are part of the Department of Justice. The Department of Justice's mission is to enforce the law and defend the interests of the United States according to the law; to ensure public safety against threats foreign and domestic; to provide federal leadership in preventing and controlling crime; to seek just punishment for those guilty of unlawful behavior; and to ensure fair and impartial administration of justice for all Americans.
The FBI, being the chief federal law enforcement agency within U.S. national borders, operates under the purview of the Department of Justice. Other departments like the Department of Homeland Security were created to deal with specific aspects of domestic security, such as guarding U.S. borders, and managing other law enforcement agencies like the Coast Guard and the Secret Service, as well as programs related to foreign violent threats and disaster response.