kami of the three main Kumano shrines
Refers to the combined deity of the three main Kumano shrines (熊野三山: Hongū, Shingū, Nachi) in the syncretic Shinto-Buddhist tradition. A specialized historical/religious term.
See also: 熊野三山
Kumano Sansho Gongen is a collective term for the deities enshrined at the three main Kumano shrines.
Refers to the three main Kumano shrines (Hongū, Shingū, Nachi) as physical sites, while 熊野三所権現 is the combined deity enshrined there.
Compound of 熊野 (Kumano, the region), 三所 (three places), and 権現 (gongen, a manifestation of a Buddha in the form of a kami). The term originates from the syncretic Shinto-Buddhist tradition of the Kumano shrines.