BioWare has released a new video on companion characters where SWTOR director James Ohlen (including some other devs) gives an in-depth look on how they will work with our own characters ingame and how they will evolve during the game. Ohlen called companions “a significant innovation to MMORPGs”, and explained what features to expect in relation to them at launch. You can read more about the companions on the official SWTOR site: http://www.swtor.com/info/systems/companions
From the SWTOR companion page:
Every Star Wars™ hero needs a companion. Han had Chewie, Luke had R2-D2 — even Jabba had the cackling monkey lizard Salacious B. Crumb. These characters complement a player’s strengths or weaknesses, and provide company for the epic journey you will inevitably undertake. Whether they’re combative, friendly, flirtatious, or even just good for a laugh, companions always contribute to your adventure.