The temples are elaborately decorated with flowers and banners; the altars are laden with offerings; vegetarian meals are provided for all; and captive animals, such as birds and turtles are set free. This is a very joyous day for everyone.
The distressed Maudgalyayana asked the Buddha, "Why is my mother suffering in the hells?"
The Buddha replied, "In her life as a human, she was stingy and greedy. This is her retribution." He advised, "Make offerings to the Sangha. The merit and virtue from this act will release your mother and others from the hells." As a result of Maudgalyana's offering, his mother and thousands of others were released from their unhappy state. After this, making offerings to release departed relatives and others from the hells became popular in Mahayana countries.
BUDDHIST FESTIVALS - http://userwww.sfsu.edu/~rone/Buddhism/footsteps.htm