The big five are the CIA, NSA, NRO, NGA, and DIA. You can start here as a branching off point: https://en.wikipedia.org/wiki/United_States_Intelligence_Communi

The big five are the CIA, NSA, NRO, NGA, and DIA. You can start here as a branching off point: https://en.wikipedia.org/wiki/United_States_Intelligence_Community https://en.wikipedia.org/wiki/United_States_Intelligence_Com... Each agency's specialty isn't always a type of intelligence, but sometimes a domain (for lack of a better word). CIA- HUMINT NSA- SIGINT NRO- space domain (shares with relevant agencies, i.e. SIGINT collected in space is shared with the NSA) NGA- GEOINT (significant presence in space as well) DIA- military domain (involved when the intelligence is militarily relevant) That's a very broad overview. The intelligence community is larger than the big five, and there are probably very few people who understand the relationship between which agency should do something vs. which agency actually does that thing.