Reviving allows a player to get another player out of the hospital, no matter how long they are in the hospital for or what their medical cooldown is. It will also replenish their life to maximum.
You gain the ability to revive once you achieve the rank of Brain Surgeon in the Medical Job. You keep this ability even if you leave the job, and it is listed as a Perk on your homepage. The most common reasons for revives are faction wars, Xanax overdoses, muggings and for getting out of hospital abroad.
Reviving costs 75 Energy, before Salutary upgrades. The faction upgrade Salutary can reduce the amount of energy reviving costs by 5 energy per upgrade. So a faction with Salutary V (5 upgrades) would make it cost 50 energy per revive, whilst the maximum upgrade of Salutary X (10 upgrades) makes revives cost 25 energy each.
You can choose if you want to receive Revives from players by changing your Settings/Preferences between 'Allow everyone', 'Allow friends and faction' (people on your friends list and in your faction) and 'Nobody'. Trying to revive a player with their settings disallowing this gives the message 'This player does not want you to revive them'.
There are honour bars 'Florence Nightingale' and 'Second Chance' for 500 and 1000 revives done, respectively. The rank 'Healer' corresponds to how highly ranked you are in revives compared to other players.