Investigation, short for Federal Bureau of Investigation.
The FBI is different from the police station. The American police are divided into three levels: federal, state and town. They don't belong to each other, and they do their jobs. The US Federal Bureau of Investigation is the Federal Bureau of Investigation, which is directly under the jurisdiction of the US Department of Justice, and exercises jurisdiction over related cases in accordance with relevant federal laws and jurisdictional agreements reached between the Federation and the states. The police headquarters works for the state government and is a government employee. Their responsibilities are clearly defined in the agreement between the state and the Federation. Theoretically, they only accept the dispatch of the state government. The name of the FBI is a special agent, and the name of the local police is a policeman. The FBI has no uniform. It usually wears a suit.
The task of the US Federal Bureau of Investigation is to investigate violations of the federal crime law, support the law, protect the United States, investigate intelligence and terrorist activities from foreign countries, implement them in leadership and law, provide assistance to federal, state, local and international institutions, and perform their duties on the premise of responding to public needs and being loyal to the US Constitution. Initially, only a few crimes were under the jurisdiction of the Bureau of Investigation. Such as land fraud, national bank fraud, anti-monopoly crime, inter-state crime and so on. But in the next few decades, the new law expanded the scope of federal investigation of national crimes. Now, every time the FBI investigates intelligence information, it will submit it to the appropriate American lawyers or officials of the US Department of Justice, who will decide whether to approve the prosecution or take other actions. Among them, the FBI has the highest priority in anti-atrocities, drugs/organized crime, foreign anti-espionage, violent crime and white-collar crime.