The Hive Mind (aka Collective Conciousness) is the connection used by the Borg Collective to link the minds of all drones together allowing a form of telepathic communication across great distances through subspace, the link also has the effect of downloading and distributing the memories, ideas, experiences, thoughts and knowledge of all members simultaniously. Following assimilation the connection to the hive mind however typically revokes the individuality of those individuals to serve the purpose of the entire Collective as a whole. One of the main advantages is near infinite processing power due to the simultanious efforts of more than trillions of highly intellectual lifeforms working together to achieve a goal. Not only are all pre-existing solutions considered however they are also capable of being creative and employing new solutions. For example when a problem is encountered the Collective will devote their full attention of all possible causes, outcomes, problems and solutions thus within seconds the best solution is then implemented. Once again using the knowledge of the members of the Collective to hastily adapt and employ the solution as quickly as possible.
The link to the Borg's collective conciousness also possesses inherent healing properties when a drone possesses any form of brain damage the neuroelectric pulses from other drones are transmitted to the damaged drone which provokes a healing effect.(VOY - "Unity")