The FBI is a US police body that works for the national government, not for one city or state. The letters stand for Federal Bureau of Investigation. Their work is crimes that break national law or cross state lines: some kinds of fraud, kidnapping across states, terrorism inside the country, and spying. A city police department handles a street fight; the FBI steps in when the crime is “federal.” Films show dark suits and a badge, and that picture is only half true — a lot of the work is slow: interviews, records, and waiting. People outside the US, including in Taiwan, sometimes say “FBI” as if it meant all American police. That is loose talk. Local police, state police, and the FBI are different offices. The CIA is different again: that one is more about intelligence, much of it overseas, not ordinary crime on a US street. Though actually the edges have blurred a little in the last twenty years, the school picture still helps: FBI = federal crime, mostly inside the country.