When shooting an ally 6/12/18/24/30% (corresponding to skill levels 1-5) of weapon damage is converted into healing. For example: An ally with a max health of 200 at 20 Health is shot by a pistol with a damage rating of 40, with Restoration at level 1 they would receive 2.4 Health per shot, at Restoration level 5 they would receive 12.
Unlike Roland's Cauterize skill, Restoration does not heal allies with grenades.
While in Fight For Your Life and being revived, Maya can shoot and heal her ally to ensure their own survival. This can be useful in the midst of an intense fire fight, where enemies may be too tough to kill for a Second Wind, to help prevent both members from becoming crippled.