In Eve Online, things can happen in a flash. A scout locates a potential target, ad-hoc tactics against it are formed. While voice comms aren't 100% mandatory in UICON, player-versus-player situations demand that pilots are in fleet and on comms when emergent gameplay happens. This is why we promote admission to the Standing Fleet and getting on Teamspeak (comms).
In organized PVP fleets there are several roles of note.
While the FC is busy moving the fleet around, the Fleet Boss controls the actual creation of Wings and Squads, the placement of commanders and boosters, and maintains the fleets advert. Fleet Commander and Fleet Boss may be a shared role.
A Fleet Commander is the most talkative individual on comms. It is his first responsibility to maintain cohesion in the fleet and order actions from commanders and scouts. The FC makes strategical decisions based on data recied from scouts and intel channels and is primary Target Caller.
The FC may appoint Target Callers, people who are explicitly requested to speak up when they recieve intel, and call for targets when the FC goes down.
Commanding positions can be given to characters capable of cascading leadership boosts.
Boosting positions can be given to pilots flying Command Ships.