Jizou or Ojizou-sama are Buddhist statues of Indian origin. They evolved from the story of Ksitigarbha, mentioned in the Sutra of the "Great Vows of Ksitigarbha Bodhisattva" - one Mahayana Buddhist sutra. It is said that the Buddha told this sutra in sign of gratitude and remembrance for his mother, Mayadevi. Ksitigarbha practiced filial piety as a mortal. In Japan, it is one of the most loved of all divinities, also related to children.
Jizou are a common sight in Japan, especially in graveyards and by roadsides. Jizou is seen as the guardian of children, particularly children who die before their parents. Their souls are unable to cross the mythical Sanzu river, because they did not do enough good deeds and made their parents suffer. Jizou save these souls by hiding them from demons in their robes. Otherwise, the souls would have to pile stones eternally on the bank of the river as penance. That is why jizou statues have sometimes some stones and pebbles nearby, placed there by people with the hope that it would shorten the children's penance.
It is also believed that firefighters are protected by jizou. Also, they are believed to protects the travellers - the dousojin or shakujin 石神, "the stone deity" - and they seldom appear along the roads.
In the photo above, there is a bowl placed in front of the jizou. People throw money from quite a distance and in case the coin falls inside the bowl, then their wish will be granted.