Not really a baseball guy, but just to add from what I know. Usually catcher is also the person who is the most knowledgeable, sometimes even more so than the ace pitcher. As he's also the one facing the outfield, a good catcher can also read the flow of the game and decide which action should be taken by the pitcher (e.g. catching someone trying to steal base) or even other defensive players (e.g. shifting defense to the side that the batter tends to hit). Catcher usually is the more "brainy" type of player, afaik.