Alan Hefner describes the Green Man:
A legendary pagan deity who roams the woodlands of the British Isles and Europe. He usually is depicted as a horned man peering out of a mask of foliage, usually the sacred oak. He is known by other names such as "Green Jack, "Jack-in-the-Green" and "Green George." He represents spirits of trees, plants and foliage. It is believed he has rain making powers to foster livestock with lush meadows. He was frequently depicted in medieval art, including church decorations.
Green George, as he is usually called in spring Pagan rites, is represented by a young man dressed head to foot in greenery, who leads the festival procession. In various festivals, Green George, or an effigy of him, is dunked in a river or pond to ensure that there will be enough rain to make the meadows and pastures green. It is also believed by some the Green Man shares an affinity with the forest-dwelling fairies since green is the fairy color. In some locals of the British Isles the fairies are called "Greenies" and "Greencoaties." In the myth of "The Fairy Children," there appears two fairy children, a brother and a sister, who have green skin and claim to be of a race with green skin.
The Green Man is linked to nature sprites and corresponds to the horned god (for example - Cernunnos, Tammuz and Damuzi, Herne, Pan, and Osiris).