Remote Healing is a collaboration technique which used by Katsuyu and its summoner using the link shared via the White Strength Seal.
Firstly, Katsuyu divides its body into several smaller clones, and then each attaches itself to a person. The user then channels their medical chakra through Katsuyu, who in turn transfers it to the wounded person, healing them. This technique allows the user to heal a great number of persons simultaneously regardless of distance. While using this technique, the user is apparently linked with Katsuyu, as witnessed by Tsunade who was able to communicate directly with the slug, and also had a sense of what Katsuyu was encountering on the battlefield most prominently displayed through her reaction to Katsuyu finding Kakashi Hatake dead on the battlefield, and later when she told Chōji Akimichi that his father was still alive after a brief pause.