From Halopedia, the Halo wiki
Restoration drones are a type of drone employed by the United Nations Space Command. They are employed for the purposes of healing and repairing friendly infantry and vehicles, alongside providing general support for ground troops.
Restoration drones are employed aboard the modified Phoenix-class colony ship UNSC Spirit of Fire. The general usage of the restoration drones manifests as a large green circle, inside which allied troops and armour are healed/ repaired through presently unknown means. The EV-44 Nightingale employs an unnamed variant of the restoration drone as part of its medical capabilities, while snipers assigned to the ship's detail operate a similar variant designed for spotting enemy targets.
Restoration drones appear in Halo Wars under the name of the Heal and Repair ability.
Halo Wars 2
List of appearances