This technique allows the user to transfer chakra to another person. For example, Tsunade and Katsuyu used this technique in tandem during Pain's invasion of Konoha, with Tsunade first transferring her healing chakra to Katsuyu, and then Katsuyu herself transferring it to the wounded villagers. Tsunade used again this technique during the five Kage's fight against Madara Uchiha to give Ōnoki some of her chakra so that he could use a massive Dust Release: Detachment of the Primitive World Technique to defeat Madara's wood clones.
Zetsu's Spore Technique creates clones, which feed on chakra to grow are also able to transfer chakra to people they come in contact with. Dan Katō was able to use this technique as a spirit in Tsunade's consciousness to restore her chakra and Yin Seal.
The Magaki Group uses this technique in a different way. First Nangō sends his chakra to Benten and Chūshin, and then both of them send it along with its own to Akaboshi, greatly enhancing the power of his techniques.
The tailed beasts are also all able to freely share their chakra with whomever they choose, and as Kurama has noted, is a less complicated process for them, than it is for humans.
