Jizo was a bodhisattva (bosatsu in Japanese), a man who achieved enlightenment but forsaked nirvana to help others find paradise. He was worshiped as the protector of those in distress, of children, of mothers in childbirth, and of travelers. Worship of the bodhisattva Jizo began in the eighth century with the importation of esoteric Buddhist practices from China. Jizo, whose name means "matrix of the earth," was revered as one of the Eight Great Bodhisattvas of the esoteric sect. Jizo and his counterpart, Kakuzo ("matrix of the void"), represent the union of the physical and metaphysical realms.
The Jizo figure is defined by his clothing, by the objects he holds, and by his physical attributes. His head is shaven, and he is dressed in monk's robes, a simple rectangle of cloth (kesa) tied in front over a longer skirt. In his left hand, Jizo holds a wish-granting jewel; he would have held a shakujo (jingle-staff) in his right. The shakujo was used to alert insects and small animals of his approach, so that he would not accidentally harm them. Jizo's idealized face and head-the perfectly proportioned features, third eye, elongated ears, and folds of skin at the neck-also show attributes of an enlightened being.
adapted from http://www.lacma.org/japaneseart/sculpture/jizo.htm