What things do the Police FBI NSA CIA and the military have in common?
They all know how to shoot a weapon.
They all use agents to gather intelligence (that is information, not wisdom) from their opponents who they are charged with defeating, and also from their fellow agencies with whom they are competing.
They're all part of the government, but that's about the ONLY thing they have in common.
Yes they may! And in some cases they may have jurisdiction in other countries ( with permission. ) to make an arrest. Although usually the State's patrol of the arrestee will make the arrest. The CIA will supervise the case while the person is prosecuted on either a State or Federal level. Usually it's also on a Federal level which where the United States Marshall's Service will step in and do the arrest and detain…
Well it depends on what you are intereseted in. The CIA is more convert information and more secretive work. This is wear spies come into play. The FBI is more like a higher police who go into more dangerous situations, they motly catch small bad guys unlike the CIA who capture terrosits and people like that. Personally I prefer the CIA.