The F.B.I. (Federal Bureau of Investigation) is the USA’s national security and law enforcement agency. They investigate federal crimes, which are crimes prosecuted under federal law rather than state law, e.g. kidnapping, bank robbery, tax evasion, counterfeiting, immigration crimes, and assassinating the president. Crimes that cross state boundaries such as mail fraud and aircraft hijacking are also prosecuted under federal law. The F.B.I. also takes on intelligence responsibilities, such as protecting the country from terrorist, cybercrime, and foreign intelligence threats.
The F.B.I. often has a glamorous role in popular media, either as the ‘good guys’ protecting the country from threats as varied as spies and aliens, or as the mysterious black-suited men who enact sinister government conspiracies.