A barony is the rank of a baron — the noble title itself. People also use it for the lands that historically went with that rank: the stretch of country a baron held. In older British and Irish history, a barony can be an area on the map, not only a word for being a baron. In Scotland, barony has a special old legal flavour tied to feudal rights, and Baron of somewhere in that sense is not always the same thing as an English peerage baron, though the words look alike. The word is formal and historical. Everyday English almost never needs it unless you are reading about nobles or old land. Though actually, barony and baronetcy are neighbours, not twins: one is a baron's rank (or lands), the other is a baronet's title.